SpongeBob SquarePants is back with a new mysterious case to solve in the second book of this exciting middle-grade series! When a glowing green trail appears outside of the Shady Shoals Rest Home, retired superheroes Mermaid Man and Barnacle Boy ask SpongeBob and Patrick to take on the case and figure out what the trail is. Unfortunately for the two detectives, they are lead through ship graveyards, underground tunnels, and ultimately in the nest of some of the most dangerous villains Bikini Bottom has ever been faced with!