Here Be Monsters! An Adventure Involving Magic, Trolls, and Other Creatures; The Ratbridge Chronicles Volume 1 Chapter 45

The Great One!

• A shaft opens up, and what's revealed inside is as big as an elephant. Tom figures it out first: it's actually a giant rat.
• And it's not just any giant rat, it's Framley, the rat that was causing all the trouble back at the pirate ship because he was so mean-tempered.
• Next a minion hits a lever, and Marjorie is zapped down to a miniature size; she manages to escape and runs under some furniture.
• Then Snatcher sends a minion to get Arthur from the dungeon to shrink next.