Alexander has just moved into Stermont, but the elementary school is being torn down, his new classroom is located in the hospital morgue, a notebook he finds is full of information about monsters--and everywhere he turns there are spooky balloon men determined to attack him.
Alexander and his new friend Rip are worried that the worms the rain has brought out are really the megaworms the Notebook of Doom describes, but they soon discover that the night crawlers are trying to warn them about the monster tunnel fish that are threatening Stermont Elementary.
The latest monsters threatening Stermont Elementary are shadowy shapeshifters that attach themselves to people, eat their shadows, and block out all light--but before he can think of a way to deal with them, Alexander has to deal with a startling revelation from his friend Nikki.
When Alexander and his friends find a very large footprint and piles of candy everywhere, they realize the school is being threatened by a Piñata-saurus Rex, a sweet-tasting monster who likes to smash things--and they find that the solution may be as near as a broken ant farm.
Alexander's class is going on a sleepover at the Stermont Museum, but something is stealing bright, shiny objects from all over town, including the museum's treasured Ruby Scorpion, and on the night of the visit the young monster hunters finally confront the town's newest monster--a warrior covered entirely by bubble-wrap.
It's a very hot summer in Stermont, and Alexander and his friends are at Camp Gloamy in the mountains, but even here there are monsters--specifically zombie snowmen called snombies who want to freeze the young monster-hunters.
It is the first day of the brand-new Stermont Elementary School, but everything electrical seems to be going haywire, and it looks like strange green lightning bugs are draining off the power--but when they see green lightning in a clear blue sky Alexander and his friends know there must be a monster involved.
Alexander's class is going on a field trip to an amusement park called Safety Land with really slow, boring rides--but this is Stermont, and when a weird magician tells Alexander and his friends that the roller coaster is haunted things start to get a lot more interesting.
Alexander keeps seeing monsters he has previously conquered, but every time he gets close they disappear and his friends are beginning to think he is delusional--but when one of their teachers turns into a blob of super-goop right before their eyes they realize the team is dealing with a shape-shifter, and it is after the Notebook of Doom.
Since the Notebook of Doom was stolen Alexander and the other monster hunters of Stermont Elementary have been operating without its assistance and now they are confronted by a large and stinky monster with eight powerful noses that can deliver a slimy sneeze with the power of a cannon--and somehow they must figure out its weakness.
The Notebook of Doom is missing and Alexander and his fellow monster-hunters Rip and Nikki are convinced that the boss-monster has it. But is that monster the mysterious Principal Vanderpants--who is certainly behaving oddly--or someone else? They need to figure that out quickly because a mistake could have deadly consequences for Stermont Elementary.
In the year since Alexander and his father moved to Stermont, he and his friends in the Super Secret Monster Patrol of Stermont Elementary have defeated all kinds of monsters, but now they face their greatest challenge, the boss-monster who has kidnapped fellow monster fighter Ms. Vanderpants and stolen the Notebook of Doom--and they have to do it before Alexander turns eight and stops being able to see monsters.