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--and they need to figure that out quickly because a mistake could have deadly consequences for Stermont Elementary.

It has been several months since monsters last plagued the town of Stermont, and frankly Alexander Bopp (leader of the Super Secret Monster Patrol) is bored, and misses his friends Rip (immersed in video games) and Nikki (soccer camp), so when his father signs him up for a summer maker program at the library he is happy to go--but soon he starts finding weird old-timey objects, and monster trading cards, and it starts to look like maybe monsters are...

Alexander is used to finding monsters everywhere in Stermont, but now the school is being turned into an icebox by giant meat-eating vegetables--and his friend Rip has gone missing.

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.

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.

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 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.

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.

Something is stealing machine parts from all over Stermont, including a wrecking ball from a local construction site, and Alexander and his fellow monster hunters, Rip, and Nikki, fear that it is building a Stermont-smashing machine--so the friends must use the resources of the summer maker program at the library to stop this monster, and perhaps even solve the mystery of who is leaving monster trading cards where the Super Secret Monster Patrol can...