The illustration on the cover shows the Monster Blood oozing down the stairs as a pair of glasses are seen.
Evan Ross, a twelve-year-old boy (who appears in all of the Monster Blood books) and his friend, Andy discover the disturbing secret about Monster Blood, novelty slime which makes people grow bigger like giants.
The book opens with twelve-year-old Evan Ross being dropped off with his creepy old aunt Kathryn for a few days, while his parents go house-hunting in Georgia. Kathryn is an eighty-year-old deaf woman, who never learned to read lips or use sign language. When we first meet Kathryn, she is busy cutting up meat in the kitchen and greets her guests with a bloody knife.
Evan has brought his cocker spaniel, Trigger, with him for company. But his aunt wants him tied up outside so that he will not chase her black cat, Sarabeth. Evan decides instead to take Trigger for a walk around the neighborhood, where he meets a cute girl his age named Andrea — who then tells him she goes by the name Andy. Evan gets excited and he readily accepts her invitation to accompany her into town. She rides her new bike quickly to town, forcing Evan and Trigger to run alongside the entire way.
Once in town, Evan quickly takes inventory of the shops. There is a video store, but he figures his aunt probably does not even have a VCR. Andy reveals that she has to buy a present for her cousin's birthday, so they stop in one of the two toy stores downtown. Inside Wagner's Novelties & Sundries, the children find a metal can with the label "MONSTER BLOOD: SURPRISING MIRACLE SUBSTANCE". The shopkeeper tries to stop the purchase and warns them not to return the tin, if they take it home and discover it does not work.
Evan takes Andy back to Kathryn's house, so they can investigate the tin of Monster Blood. Andy thinks Kathryn's house is super cool and dreams about being able to read all the leather-bound books on magic that line the shelves. Upstairs, the children uncap the tin and discover a glowing green substance. It bounces, glows in the dark, and is cool to the touch. Because the Monster Blood leaves stains on the floor and wall, they decide to take it outside. They roll the blood up into a ball and bounce it back and forth amongst themselves. Finally, Trigger grows weary and decides to eat a gob of Monster Blood.
The next morning, Trigger is not feeling well. So Evan treks out into the neighborhood by himself. He runs into two fourteen year old twins dressed in black. Rick and Tony Beymer harass the wimpy Evan, who tries to joke with the two bullies in means of coming out unharmed. Luckily for Evan, Andy comes to his rescue and she tries to scare away the twins. Which only results in them turning their attention to pestering her. Thankfully, the twins just swipe her bike and do not hit her, but she does get knocked down in the scuffle. Evan does not bring attention back to himself and Andy runs home to clean her scraped leg.
Back home, Evan finds Trigger choking in the backyard. It seems either the dog's grown larger or the leash has grown smaller. They discover the tin of Monster Blood is now overflowing with the green goop. Also, the gelatinous substance is no longer cool to the touch, but instead feels disturbingly warm. This is not enough however to discourage the children from having a Monster Blood fight. The two fling Monster Blood at each other inside Evan's bedroom. But then they start cleaning up the mess, when they suddenly hear a horrifying howl from down below. Evan rushes to the window with Andy right behind him and she points out that Trigger has doubled in size!
The dog, who is now the size of a pony, rushes out of the backyard. Evan and Andy try to run after it, but they do not get very far before Trigger turns into a horrible monster. And then Evan wakes up from the dream! He slowly realizes that the bed he is in is too small. He is a giant monster or something! Then he wakes up again...
Evan and Andy take Trigger to the vet in order to get him check out. But the doctor tells them the dog is having a rare growth spurt and then sends them on their way. Andy then rushes off to her piano lesson.
Left alone, Evan decides to buy himself an ice cream treat at the local market. He leaves Trigger tied up outside. When he returns with his ice cream sandwich, Ricky and Tony are stealing his dog. Trigger gets angry and once let loose, chases after the twins. Evan becomes terrified as he remembers how this happened in his dream and he begins to worry that he might turn into a monster, just like in his second dream.
Back home, Evan calls Andy and asks if he can see her, claiming it to be an emergency. Upon arriving, he shows Andy the full bucket of Monster Blood, before pleading with her to take some of it. She agrees to take a coffee cans worth. However, when she scoops the can into the bucket, the Blood scoops back. Andy freaks out as the Blood sucks the can right into the middle of the bucket. When Evan fishes his hands in to retrieve the can, he tells her he can feel the suction, like it is alive!
As Evan is leaving Andy's house, the twins surprise him by beating him up. Andy helps Evan scoop the Monster Blood back into the overturned bucket, then comes up with a foolproof plan: they'll just return the Monster Blood to the toy store.
Evan sneaks back home and realizes he needs to find a new container for the ever-growing Monster Blood. He empties the bucket into an old bathtub in the garage. Suddenly Sarabeth, the cat, pounces on him and he falls into the tub of Monster Blood. Evan narrowly escapes getting sucked into the muck.
The next morning at breakfast, Evan decides he has to tell someone else about the Monster Blood. He writes Kathryn a brief note on a legal pad and she just laughs at him and his imagination. Evan calls Andy to see if she is ready, which she suggests he use a plastic lawn sack to carry the Monster Blood. The two drag several lawn bags worth of breathing Monster Blood down several blocks to the toy store, which turns out to be closed...forever!
The two lug the sacks all the way back to Kathryn's house and empty the lawn sacks into a metal garbage can. As soon as they clamp shut the lid, Kathryn runs out of the house waving a yellow sheet of paper. Evan's mother just sent a telegram that she will be coming to pick him up that day.
Evan is so excited that he runs to tell his dog the good news. When Evan opens the gate, he sees that Trigger has actually doubled in size. The beast leaps out of the backyard and into the streets. Evan runs after him but trips and knocks the trash can over. The large mass of Monster Blood spills out and tries to swallow him. Evan moves out just in time and he and Andy run down the street as the large rolling ball of Monster Blood moves quickly after them.
They run into the twins, and they are shortly swallowed up by the Monster Blood. The children stop to stare at the still outlines of the twins' bodies inside the giant heap of Monster Blood. The children split up so that at least one of them have a chance, but Kathryn chooses this time to stick her head out of the house. The Monster Blood rolls into the house after Kathryn.
The children run into the house to save Kathryn and find her trapped in the corner, the huge round blob of Monster Blood about to engulf her. She cries out that she is responsible for the Monster Blood and she will have to pay with her life. Evan accuses his great-aunt of trying to kill him by casting a spell on the Monster Blood but she insists it wasn't her who put the spell on the Monster Blood. She points towards the other side of the room and cries out, "It was her." She is pointing to Sarabeth the cat, who then transforms into a beautiful young woman wearing a black cape.
Kathryn explains that twenty years ago, Sarabeth cast a spell on her that made her a slave. She also made her deaf and refused to let her learn sign language or lip-read so she could control her better. Sarabeth did not allow Kathryn to have visitors. So when Evan showed up, Sarabeth insisted she cast a spell on the Monster Blood to get rid of him. Kathryn tells Sarabeth that she is going to end the spell by letting the Monster Blood swallow her, thus ending Sarabeth's hold on her. Sarabeth tells her that she is still going to kill the children and raises her hands to command the Monster Blood to kill them and they brace for their on-coming deaths. Suddenly Trigger leaps through the door, pushing Sarabeth into the Monster Blood.
Sarabeth is completely engulfed in the ball of Blood and soon Trigger quickly shrinks back down to normal size and the children look over at the dwindling ball of Monster Blood. The two twins get spit out and they immediately run from the house. Just as Evan's mother wanders in and asks why those two boys were running from the house.
Andy and Evan say their goodbyes soon after. Evan tells her he would like to write to her, while she mentions she can call him with her father's phone card. But she then asks him for just one favor: she would like to keep some of the Monster Blood as a souvenir.
When they go to collect the Monster Blood, they discover it has vanished.
Cover Art Gallery
To coincide with the release of Monster Blood for Breakfast!, Scholastic reprinted the original Monster Blood book for the Classic Goosebumps series. This time with added bonus features. It also features a raised cover.
- R. L. Stine has stated that he was inspired to writing the story after his son used to play with his toy slime.
- In the television adaptation, it had a second part called More Monster Blood. Evan is in a plane telling this story to some newfound friends. They start to wonder what would've happened if some monster blood came aboard the plane. Meanwhile, in the storage Trigger starts barking at Evan's suitcase as some monster blood spills out...
- Nintendo is mentioned by name in the book.
- The Dutch version of the Monster Blood had a few differences from the original book.
- Evan was replaced by a girl named Steffie and Andy was replaced by a boy named Mathijs.
- In the American version Sarabeth was the main villain, but in the Dutch version, Sarabeth was a hypnotized cat and Kathryn was an evil witch.
- The twins never got spit out. This means that they are dead.