An imaginative mouse who likes to read heroic fantasy novels finds herself on the school math team as it prepares to compete for the coveted Golden Slide Rule.
Before the Mighty Mighty Monsters can play Hide and Seek, they need to make some rules such as no flying like a vampire bat, no sniffing like a werewolf, and no using magic.
While on a trip on a huge cargo ship to a deserted South Seas island, orphans Henry, Jessie, Violet, and Benny Alden discover the island is not deserted at all.