Enter HorrorLand was a continuing story that was throughout books 1-12 of Goosebumps HorrorLand. The story featured the kids from the first 10 books all going to HorrorLand, having scary encounters, and meeting and teaming up to defeat their old enemies and a new enemy named The Menace. Books 1-10 had the regular story, but had a few chapters at the end of the book that continues the Enter HorrorLand story. Books 11 and 12 conclude the story with the kids escaping to Panic Park and trying to defeat The Menace and escape Panic Park to go home as well.
Britney and Molly are excited about going to visit HorrorLand. Molly briefly questions how HorrorLand knew to invite her along with Britney's family. However, Britney's father insists it is normal for theme parks to know a lot about people.
Upon entering the park, the Horror working the ticket booth pretends to eat the girls' invitation. The Horror can't admit the family until he makes every member scream so they can log it for identification purposes, which he achieves by burning their luggage with a flamethrower. Another Horror pulls up in themed cab and drives the family at quick speed through HorrorLand. They pass many, many punned attractions, then the driver soon crashes the taxi and they come to a stop.
Everyone gets out to wander the grounds, while looking for their on-site hotel. Britney and Molly check out a mask shop that ominously features masks of their faces! The family eventually finds the hotel, which of course is called the Stagger Inn. While waiting for their rooms, a renegade Horror tells the family that they are in danger. The helpful Horror pleads with them to escape while they still can and find the "other park"...
The hotel's guide, Druella, leads Britney's parents to their room on the second floor, then takes the girls up to their private suite on the thirteenth floor. The girls are delighted to see an awesome room. The room has a flat-screen television and plenty of clothes in their size but no mirrors! The girls are so excited that they want to tell their parents, but the girls cannot find them anywhere. Both girls go to the main counter. The Horror working behind it informs them that Britney's parents checked out.
When the girls go back to their parents room, they find a single camera, which contains a picture of Slappy.
Later in the summer, Billy and Sheena receive a free invitation to the HorrorLand theme park. Neither of the siblings know why they were chosen to go, but both they decide to go to HorrorLand anyways.
After spending the morning meandering through HorrorLand, Billy and Sheena go back to the Stagger Inn. In the lobby, Billy notices two girls, Britney Crosby and Molly Molloy, who look very distressed. When Billy and Sheena talk to them, the girls say that their parents are missing. Billy and Sheena say that the same thing happened to them, but they overheard a Horror saying that their parents had simply been moved to another hotel in order to scare the kids. Britney is still confused by her picture of Slappy, but when she searches for it, it is gone.
The four kids decide to explore HorrorLand and they go to Quicksand Beach. Billy becomes scared when he and his three acquaintances begin drowning in quicksand. As Billy sinks, he hears the chanting of pirates... However, before Billy drowns, he realizes that he is in a waterslide. At the end of the slide, a Horror pulls Billy off, and he is reunited with Sheena but not Britney and Molly. Billy and Sheena start looking for Britney and Molly, and they end up going to The Play Pen. In The Play Pen, they see a boy who wields a gray card and wins every game. The kid is spotted by the Monster Police, but before the police can catch him, he gives his card to Billy and runs off.
Later, back at the Stagger Inn, Billy and Sheena run into the boy from earlier. He says his name is Matt Daniels and that the card was lucky and that it was given to him by a Horror. The three kids go in search of Britney and Molly. The group sees Britney and Molly inside of a locked restaurant. They use Matt's gray card to unlock the door, but when they get inside Britney and Molly are gone, and, more shockingly, Sheena becomes invisible.
Matt Daniels and Billy Deep are trying to help Sheena Deep from being invisible forever. They try to get help from two Monster Police members, Benson and Clem, but the only thing they do is force Billy and Matt into a X-ray machine to see if they have a room key card, which Matt has.
Matt tricks the Horrors that he doesn't have it when he goes through the machine. Since Sheena is invisible, Matt secretly gives her the card, and Sheena hides it in her hand.
They escape the Horrors, or not. The two Horrors start chasing them. Matt, Billy, and Sheena goes inside "Dr. Twisted's Science Lab" to hide from the Horrors that were chasing them.
Billy accidentally opens a box of Monster Blood, which swallows Billy and Sheena. Matt just stares at them, horrified. Byron unexpectingly enters the lab, and helps get the Monster Blood off of them by using a mirror, which sucks the Monster Blood into the mirror. Sheena disappears afterwards. Byron is caught by Clem and Benson and gets taken away.
Carly Beth Caldwell receives an invitation to HorrorLand in the mail, and she decides to go and take her best friend, Sabrina Mason, with her. While attending Mondo's magic show in HorrorLand, Carly Beth and Sabrina see Billy Deep and Matt Daniels. Carly Beth and Sabrina talk to Billy and Matt, and the girls find out that Matt and Billy are in search of Sheena Deep, Britney Crosby, Molly Molloy, and a Horror named Byron.
The magic show starts and Billy is surprised when Mondo makes his sister Sheena, appear onstage. Sheena says that, before reappearing onstage, she saw Britney and Molly on a flaming carousel in a dream. Matt warns Carly Beth that she is a special guest, and she is likely in danger. The kids sneak backstage and find Byron's name tag on the floor alongside a small flyer for a ride called the Wheel of Fire. The kids go in search of the ride, but Carly Beth is startled when she passes the HorrorLand mask shop. Carly Beth sees the Haunted Mask though the window. Carly Beth and Sabrina go inside the shop, and they find masks that look like Britney And Molly. The masks whisper vague warnings to Carly Beth. Carly Beth screams, but the Horror tending the shop tells her that a draft was causing the masks' lips to move.
After leaving the shop, the girls hear two Horror MPs, Bubba and Marcus, discussing scary surprises for all of the special guests. Marcus says that two special guests (Britney and Molly) have already been dealt with.
The two girls rush off in search of Matt, Billy, and Sheena. As the sun is setting, Sabrina and Carly Beth rush into Wolfsbane Forest in search of the other kids. The girls get lost in the woods as night is beginning to fall. The girls hear wolves in the distance and footsteps nearby. Suddenly, a dark figure leaps out at them...
Robby Schwartz receives an invitation for HorrorLand in the mail. Despite Dr. Maniac's threats, Robby decides to go. In HorrorLand, Robby becomes lost in Wolfsbane Forest. He accidentally stumbles into and startles Carly Beth Caldwell and Sabrina Mason, two girls who are also lost in the forest. Since the main exit is locked, Robby digs a small hole along the edge of a fence. The kids all crawl through the hole. Once they escape the woods, Carly Beth and Sabrina explain how all of the special guests were in danger.
Robby is helping Carly Beth and Sabrina, but he is distracted and separated by an arcade. There, Robby sees a Dr. Maniac video game. Robby is inexplicably draw to the game. Robby does not want to play it, but he is unable to resist the urge to play. Robby is pulled away from the game by two girls, Britney Crosby and Molly Molloy. They reveal that they want to go to Panic Park. Molly shows Robby a gold coin, and Robby feels as if the coin is hypnotizing him, so he bats the coin out of Molly's hand. The coin lands in front of the door to the arcade. Just as the coin falls, Slappy enters the arcade. Slappy grabs Robby and demands that Britney retrieve the token and use it to hypnotize Robby. When Robby gazes into the coin, he blacks out, only to reawaken on the floor of the arcade with Carly Beth and Sabrina staring down at him; Molly and Britney are gone. Before leaving with Carly Beth and Sabrina, Robby picks up the gold token.
During Abby's first night in the Stagger Inn, she dreams that a mummy is in her room. Abby screams and wakes up. She sees muddy footprints in her room and yellow gauze. A boy named Michael Munroe knocks on her door. He says that he is from the next room over and he was concerned when she screamed. The two become friends and they agree to explore the pro together the following morning.
The next day, the two kids meet a horror named Byron. Byron gives the kids an note telling them that they should leave because they are in danger. Abby gets an invitation to the Vampire Café, so she decides to go. She sits next to Carly Beth, Sabrina, Matt, Billy, and Sheena. Michael sits next to a kid named Robby. Abby explains that she saw Byron, and the other kids are surprised by this. Robby mentions that he saw the missing girls while he was in the arcade. Robby shows off the Panic Park token that he had picked up, but a waitress takes it.
The kids leave and they are met by Byron. Byron gives them all HorrorLand tokens. Abby has a pyramid on her coin. All of the kids have a different design on their coins. Before leaving, Byron says, "Inside the Bat Barn. Four o’clock sharp." Later, Michael pulls a tracking chip off of his coin. All of the kids give their coins away to passing guests except Carly Beth and Sabrina. The kids go to the Bat Barn, and Abby finds a flyer for the Mirror Mansion. Inside the Bat Barn, the kids are swarmed by bats, and they cannot find Byron.
Michael Munroe, Abby, Robby, Carly Beth, Sabrina, Matt, Billy, and Sheena are all being swarmed by bats in the Bat Barn. Michael was invited to HorrorLand by a letter, but HorrorLand ended up being different than he imagined. Michael uses his dog whistle to scare off the bats. The kids leave and they are confused as to why Byron had told them to go to the Bat Barn. Matt and Michael begin fighting, but several Monster Police members break up the fight. Matt and Michael apologize, and the group explains everything that happened. The kids all notice the lack of mirrors in the park, so they suspect that having a mirror may be important.
Michael goes in search of a mirror, and the rest of the group goes in search of Byron. The group plans on meeting up at the Stagger Inn in two hours. Michael finds and enters a tunnel that has a "DO NOT ENTER" sign. Michael finds robots. He is stopped by a Horror and told to leave. Michael and the other kids meet up, and Michael takes his laptop and the kids back to the tunnel that he had been thrown out of. Michael manages to get an Internet connection in the tunnel. Michael finds out that HorrorLand was built in the mid-1970s. The creator of the park was Kit Katzman. Michael searches for Panic Park and he finds that it was built in the 1950s by a man named Karloff Mennis. Michael find out information about Panic Park. Apparently, the park's most popular attraction was the Wheel of Fire. Michael then reads a blog by Luke and Lizzy Morris, two former HorrorLand guests. An alarm goes off in the tunnel and the kids flee. Carly Beth suspects that the tracking coins that Byron gave them had given their positions away. The kids duck into a lab that is filled with gorilla-like creatures. Members of the Monster Police corner the kids in the lab. Michael uses Matt's keycard to release some of the gorilla-like creatures. With the Monster Police distracted, the kids run away.
The kids go to Good-Bye Land because Michael suspects that there may be an exit there. Benson and Clem of the Monster Police, pull Michael into the bushes. They warn Michael not to leave. A third Horror with no name tag shows Michael a mirror. Michael is sucked into the mirror. Michael reawakens in Panic Park.
Julie Martin gets an invitation to HorrorLand in the mail. In HorrorLand, Julie tries to take a photo of a booth using her new digital camera, but a ventriloquist dummy is visible in the background. Shortly after this, Julie sees large monsters coming out of a sewer grate. The monsters charge at Julie, but multiple Horrors intervene. Julie overhears a Horror say that kids had set the monsters free.
Julie finds seven other special guests: Billy, Sheena, Matt, Carly Beth, Sabrina, Robby, and Abby. They warn Julie that she is in danger. The kids all run through the Tunnel of Screams in order to avoid the Monster Police. When Julie exits, she cannot find the other kids. Julie finds meets Byron, and Byron hands her a hand mirror wrapped in paper and warns her about someone named The Keeper. Julie throws away the mirror, and she meets back up with Abby and the other kids. The kids leave in search of the mirror. Julie is not able to get back to the trashcan before a Horror empties the trash.
The kids head toward an exit. Surprisingly, a Horror lets the kids leave after he stamps the kids' hands with a readmission stamp. The kids exit, but the stamps on their hands begin to feel strange. The stamps grow in size and begin shooting out purple tendrils. The stamps slowly wrap around the kids.
Boone gets an invitation to HorrorLand in the mail. When Boone get's to HorrorLand, he sees multiple kids entangled in purple tendrils. Boone quickly becomes entangled in the tendrils when he tries to help. A Horror approaches and frees the kids. The Horror takes the kids on a bus and Boone meets Julie, Billy, Sheena, Matt, Carly Beth, Sabrina, Robby, and Abby. The kids ask the Horror where they are being taken, and the Horror tells them that he is taking them to The Keeper.
Boone pretends to be attacked by a snake. Boone's act is so convincing that he scares away the Horror's on the bus. The kids run to Good-bye Land. The kids go on a ride called the R.I.P.P.E.R. DIPPER; the kids want to go on the ride because the ride goes underground, and they want to get to into the HorrorLand tunnels. When the kids get underground, they are captured by several Horrors. The Horrors take the kids to Mondo's shop.
Inside the shop, there are stairs. The Horrors lead the kids down the stairs to a room where The Keeper is supposed to be. The Horrors leave and the kids are all scared by items in the room. The room contains the Haunted Mask, a mummy, a camera, and an oil painting of Captain Ben. Robby is terrified when Dr. Maniac enters the room and reveals that he is The Keeper. Soon, the Purple Rage enters the room. The kids learn that he is working with Dr. Maniac, and the kids deduce that all of their enemies were working together as a part of a group revenge plot.
Jillian and Jackson Gerard get an invitation to HorrorLand in the mail, and they decide to go. The kids hope that they will find something that explains their psychic powers in HorrorLand. The kids find Madame Doom's fortune telling booth. The machine dispenses a card saying "ESCAPE HORRORLAND." The kids are stopped by Inspector Cranium. Before Inspector Cranium can enact his revenge, the kids run away. Jackson lifts Madame Doom and throws her at Inspector Cranium. This allows the kids to escape to the Doom Slide. The kids ride the slide, but they are met by several Horrors at the bottom of the slide. The Horrors take the two kids to The Keeper.
The kids are taken into a shop and moved downstairs. The siblings see a group of kids as well as a villain wearing leopard skin (Dr. Maniac) and a purple villain (the Purple Rage). Jackson uses his psychic powers to throw a chandelier at the Purple Rage, which liquefies the Purple Rage. Dr. Maniac scares the kids by making the room extremely hot and then extremely cold. The room gets so cold that Robby falls to the ground, and the others assume that he has died.
Dr. Maniac becomes distraught by this; as The Keeper, Dr. Maniac is supposed to keep, not kill. Dr. Maniac says that someone named The Menace will kill him, so he runs away. Robby gets off of the ground and reveals that he was only pretending to be dead. The kids are able to escape, and they begins searching for a mirror. One of the kids, Matt, uses a keycard that Byron had given him to enter a restaurant filled with mirrors. Five kids manage to jump through the mirrors, but the remaining six kids (Matt, Carly Beth, Julie, Robby, Jackson, and Jillian) hit solid glass. Several members of the Monster Police chase the kids away. The six kids meet two new kids; Luke and Lizzy Morris. Luke And Lizzy say that they are not working for the Horrors, but Jillian reads their minds and determines that they are lying.
Lizzy and Luke Morris are being surrounded by six of the Very Special Guests (Matt, Carly Beth, Julie, Robby, Jackson, and Jillian). Lizzy tries to warn the kids that they will be in more danger if they go to Panic Park. The kids do not believe Lizzy or Luke. The kids see Byron, and he tells the kids to get to Panic Park. Byron takes the kids to the Hall of Mirrors and leaves them there. The kids walk through the one of the mirrors. The kids are transported to Panic Park, and they are surprised to see that everything in the park is in grayscale. The kids talk to a family. The family says they had been in Panic Park when it disappeared, and when Panic Park disappeared, all of the people in it disappeared and turned into shadows.
The kids find a newspaper clipping that says that Panic Park was supposed to be torn down in 1974. The kids search an information booth, and they find a strange dummy named Rocky behind the booth. The dummy shrieks at them and tells the kids that the park is closed. The kids leave in search of the flaming carousel. The kids see Billy and Sheena Deep on top of a fake mountain. The kids begin climbing the mountain, and the mountain almost breaks beneath them. Jackson uses his psychic powers to pull Billy and Sheena down. Billy and Sheena say that they were separated from the other kids in the Tunnel of Hate, and they wanted to get to a high vantage point to look for them.
The kids go to the tunnel. Inside, the kids all begin fighting and calling each other names. The group finds several of the other Very Special Guests, but the other Very Special Guests have been in the tunnel so long that they have turned into hateful beasts. Jackson uses his psychic powers to remove the kids from the tunnel. The kids find Byron. Byron says that the kids can escape if they follow him. Byron takes the kids to the Midnight Maze, and he says that there is an exit inside the maze. The kids begin to doubt Byron, but Jillian says that she read his mind and that Byron is not lying. Soon, the kids come across giant eggs. Michael says that he recognizes the eggs. Giant monster emerge from the eggs. Michael goes over to the yolk of the egg and drinks some. Michael transforms into a monster and defeats the other monsters. Micheal eats more of the yolk and transforms back into a human. The kids are approached by floating masks, and Carly Beth recognizes them. Carly Beth is unable to resist grabbing and putting on the Haunted Mask. Then, Carly Beth grabs the other masks and tears them in half. Sabrina remembers that it takes an act of love to remove the Haunted Mask, so Sabrina kisses Carly Beth on the cheek and removes the mask. The kids keep walking, and they come across a beach and a large body of water. The kids see a giant pirate ship in the distance, and Billy and Sheena appear terrified. The kids find a rowboat, and they all climb in. They plan on rowing to the other side of the body of water, but they want to avoid the pirate ship.
While paddling, the kids lose control of the boat, and the boat begins going towards the pirate ship. The kids' boat is commandeered, and the kids are taken aboard the pirate's ship. The kids are thrown overboard by Captain Ben and his crew. When the kids meet the water, they sink down to a tunnel at the bottom of the lake. The tunnel pulls the kids through to the other side of the lake. The kids leave the beach and keep walking until they find a sign for HorrorLand. The kids are met by multiple Horrors, and the Horrors tell the kids that they are still in Panic Park. The kids want Jillian to read the Horrors' minds, but she says that she cannot read the minds of Horrors. Lizzy says that Jillian read Byron's mind, so she had to be lying. Matt accuses Jackson of lying as well. Suddenly, a man approaches, and he reveals himself to be Karloff "The Menace" Mennis, the creator of Panic Park. He says that he needs the kids to stay in Panic Park forever.
Lizzy, Luke, and the Very Special Guests are brought before a giant stage and The Menace tells the kids that someone tricked them into coming to Panic Park. All of the kids turn to Jillian and Jackson Gerard. The Menace reveals that Jillian and Jackson's psychic powers did not come from Madame Doom, but their powers came from him. Billy Deep tries to escape the auditorium that all of the kids are being held in, but shadow people are blocking the exit. When Billy Deep leaps through the shadow people, he comes out looking as though he is in grayscale. When the kids beg The Menace to change Billy back, The Menace refuses.
Several shadows approach the kids and put bracelets around their wrists. The Menace says that the bracelets will collect the kids' fear. The Menace calls for the Fear Meter, and Byron brings it to him. The Menace reveals that Byron has worked for him all along. Byron says that he chose the bravest kids possible because only the bravest kids will be able to survive The Menace's tests. The Menace says that he will use the kids' fear to remove Panic Park from 1974; in 1974, the Fear Levels in Panic Park were so high that the entire park was shifted into another dimension. The Menace then reveals that he has two faces; one face is normal, but the other face is bright red and acts insane.
The Menace begins the Fear Meter. The Fear Meter says that the kids' fear level is only 20, and The Menace wants the number to go up to 100. The kids all fall through a trap door in the floor, and the land in a screening room. The Menace plays a recording of a roller coaster, and the chairs that the kids are sitting in tilt in sync with the tilting of the roller coaster in the film. After several more scares, Byron takes the kids from their chairs and moves them to the room where they will be staying.
Once Byron has left, the kids open the door to their room and find that it is unlocked, so the run out into the hall. The kids find an elevator and enter it. The lights in the elevator go out suddenly, and the elevator begins free falling. When the elevator lands, the kids cannot manage to open the elevator doors. Eventually, the doors slide open on their own. The kids run outside into Panic Park. Once outside, Carly Beth is surrounded by shadow people who demand hugs. The shadows envelope Carly Beth and cause her to turn into a shadow. Meanwhile, Robby remembers that Britney and Molly had visited him in HorrorLand, so he asks the girls how they escaped Panic Park. The girls cannot remember the exact method for escaping, but they remember entering a white building. The kids go to a nearby white building. The inside of the room looks like a waiting room. Unexpectedly, Dr. Maniac appears. Dr. Maniac checks the Fear Meter and sees that the meter reads 50.
Dr. Maniac uses a giant paint brush and brushes it over Robby. Dr. Maniac uses the brush to erase Robby. Dr. Maniac leaves. Robby, now invisible, and the other kids continue searching for the building that Britney and Molly had used to escape. Sheena sees the Hall of Mirrors, and the kids deduce that they can use the mirrors to get back to HorrorLand. The kids are unable to pass through the mirrors and the doors to the building slam shut behind them. Many horrible things appear in the reflections of the mirrors surrounding the kids. Eventually, Slappy appears in one of the mirrors. Slappy zaps Britney, which causes Britney to turn into a ventriloquist's dummy. The Menace reappears, and he criticizes the kids for not being frightened enough. Michael stands up to The Menace, but the Menace decides to use Michael as an example. Suddenly, there is a bright flash. After the flash, the kids find that Michael now has a second face. The kids manage to run away from The Menace. The kids stumble across all of their enemies from earlier in the year!
However, the villains do not attack the kids. The villains instead explain that they were hired by The Menace to scare the kids out of HorrorLand. However, the villains say that Ned, also known as Monster-X, was trying to help the kids by giving them information. Inspector Cranium reveals that he read the mind of The Menace. He says that The Menace plans on keeping the kids and the villains in his park as prisoners. The villains offer to team up with the kids. The villains say that if the kids stand up to The Menace, their Fear Levels will go down. Reluctantly, the kids agree to stand up to The Menace.
The villains lead the kids to a building where The Menace is. The kids wander into the building and approach The Menace in his study. Byron jumps out and tries to stop the kids, but the kids push him out of the way. The kids all join hands and begin chanting together. The menace jumps up and the Fear Meter reaches 97. The Menace moves over to his computer and begins typing. Worms begin crawling out of the kids' nostrils, mouths, and ears. The Fear Meter now reads 99. Lizzy gets an idea, she tells Luke a joke. They begin giggling and telling each other jokes. Eventually, all of the kids start laughing and the Fear Meter begins dropping. All of the other villains enter, and they begin laughing at The Menace as well. As everyone laughs, The menace begins shrinking and melting. Soon, everyone becomes aware that The Menace's Panic Park is shrinking. The villains and the kids leave The Menace and run to the ride called The Whirlwind. The kids believe that the ride is dangerous, but the villains say that the ride will take them to HorrorLand. With no other options left, the kids get on the ride.
The kids arrive back in the HorrorLand parking lot; Britney is no longer a dummy, Carly Beth and Billy are no longer shadows, Robby is no longer invisible, and Michael has only one face. The kids are reunited with their parents. The parents of the kids do not have any clue that their kids had been in serious danger. Lizzy observes a Horror watching them, and she asks if he is Ned. The Horror confirms Lizzy's assumption, and Lizzy thanks him.
Once she is back at home, Lizzy is unable to forget Panic Park. In her suitcase, Lizzy finds Slappy. Slappy smiles and asks if Lizzy is ready to start a new story.