The cover shows a monster hatching out of an egg.
Michael Munroe really hates his teacher, Mrs. Hardesty. Michael knows that she totally has it out for him. One day Michael sneaks into Mrs. Hardesty's house to pull an awesome prank on her. However, Michael finds a six-foot-egg in Mrs. Hardesty's attic, and Mrs. Hardesty is planning to hatch it!
This story begins with Michael "Monster" Munroe, Daisy Edwards, and DeWayne Walker sneaking into the house of their superstitious teacher, Mrs. Hardesty. They plan on scaring their teacher by leaving a black cat in her house. Their teacher returns home, and the story suddenly jumps back to two weeks earlier.
In class, Michael scares Mrs. Hardesty by repeatedly opening the window shades; Michael attached an audio sensor to the blinds at the beginning of class, so whenever he blew his dog whistle, the window blinds flew open. Michael drops his whistle, and Mrs. Hardesty sees it. Michael, Daisy, and DeWayne gets in trouble and have to stay after school. Mrs. Hardesty says that the kids can stay after school for a week or do community service on Saturday. The kids begrudgingly agree to the community service. Their principal, Mr. Wong, stops by Mrs. Hardesty's classroom and he tries to tell her that she is being too harsh, but he cannot persuade her. On Saturday, Mrs. Hardesty demands that the kids dig through a dumpster and hunt for recyclables. After their community service, Michael swears revenge. He begins formulating a plan; he will scare Mrs. Hardesty by hiding a cat in her basement.
The story jumps back to Michael, Daisy, and DeWayne inside of Mrs. Hardesty's house. Michael accidentally drops his dog whistle while running through his teacher's house, but he does not pick it up. The kids venture into the attic and let their cat loose. Mrs. Hardesty comes home early unexpectedly, so the kids decide to stay quiet. The cat meows loudly, so Mrs. Hardesty enters the attic. The kids hide before the teacher can see them. Michael sees Mrs. Hardesty reveal six foot tall egg. Mrs. Hardesty then sits on the large egg. Mrs. Hardesty falls asleep, so the kids have to sneak out. The next day at school, Mrs. Hardesty says that she found a black cat in her house, and she was very distraught by this. Mrs. Hardesty seems to suspect Michael, but she does not punish him.
Michael is so intrigued by Mrs. Hardesty's egg that he sneaks back into Mrs. Hardesty's house. Michael hides behind the couch in her attic. Michael's teacher enters the attic and climbs onto the egg. The egg begins cracking. A large scaly monster emerges from the egg. Mrs. Hardesty calls the creature her baby and cleans off the creature. Mrs. Hardesty moves the monster to the basement. In the basement, Mrs. Hardesty opens a door and reveals many more monsters. She also assured the creatures that they will take over Earth. Mrs. Hardesty tells her "babies" that they need to lay more eggs. She also says that she will feed some of the eggs to the kids at school. Mrs. Hardesty also reveals that her real name is Hyborg-Xrxuz. Michael sneaks out and goes home.
The next day, Michael goes to Mrs. Hardesty's and, through her kitchen window, Michael sees Mrs. Hardesty eat an egg and turn into an alien monster. She eats another egg and changes back. Mrs. Hardesty exits the kitchen and approaches Michael. Mrs. Hardesty brings Michael into her house, and she force feeds him eggs. Michael begins turning into a monster. Mrs. Hardesty leads Michael into the basement, and she puts him with the other monsters. Eventually, Mrs. Hardest leaves. Daisy and DeWayne enter Mrs. Hardesty's house in search of Michael. Daisy and DeWayne are shocked when they find all of the monsters. Michael tries to show Daisy and DeWayne that he is not actually a monster. Unable to talk, Michael finds his dog whistle and uses it to prove that he is actually Michael. The three head back to the kitchen. Michael finds some egg left in the kitchen, so he eats it and begins transforming back. However, Michael's arms and chest stay green because he he did not eat enough eggs. The kids plan on going to Mr. Wong's yard. While going to their principal's house, the kids notice that they are being followed by the other monsters. The kids find Mr. Wong in his house sitting on an egg. Mr. Wong is asleep, so he does not see the three kids. The monsters that had been following the kids block the exit. Suddenly, Mrs. Hardesty appears with a tray of eggs. The kids hide behind a couch before their teacher and principal can see them. Mrs. Hardesty addresses Mr. Wong as Commander Xannx. Mrs. Hardesty sees the three kids hiding. Mrs. Hardesty commands her monsters to attack. Enraged, Michael cracks the egg Mr. Wong is sitting on, and he falls into the egg. Then, Michael lifts and throws Mrs. Hardesty into the cracked egg using his monster claws. The teacher and principal turn back into monsters. Unable to swim, the two monsters drown in the egg. The other monsters dive towards the cracked egg and they begin eating parts of it. As the monsters eat, they begin transforming back into egg yolks. Michael eats some of the egg and his arms and chest return to normal. The kids leave the house.
Michael returns home and eats dinner. After dinner, Michael's mom brings out a cake. Michael begins eating it. Michael's mom mentions that the cake was made by Mrs. Hardesty, and Mrs. Hardesty had used some "special eggs" while making the cake...
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 creatures. Members of the Monster Police corner the kids in the lab. Michael uses Matt's keycard to release some of the gorilla 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. Two Horrors, Benson and Clem, 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.