When the Alden children and their grandfather visit Everglades National Park in Florida to solve the mystery of a missing ranger, they discover that a panther provides a clue.

Emmet Doyle is not in the best mood when he arrives in Florida City. His father is a wildlife biologist, and has been summoned to the Everglades, dragging Emmet along with him. Though still in mourning from losing his mom a year ago, Emmet's trying hard to keep a good attitude. Upon their arrival, however, things quickly get weird. Dr. Rosalita Geaux, the Park Superintendent, wastes no time in revealing the reason she called Emmet's father to Florida....

After a concussion that effects her balance, memory, and other abilities, twelve-year-old Kat goes to I-CAN, the "Miracle Clinic in the Swamp," where she joins forces with other patients to expose plot that endangers them all.

Time has passed since anyone's heard from Dr. Catalyst. Emmet and Calvin have even begun to think that the crazed scientist might be gone for good. But then, on a trip to snorkel off the Florida coast, one of their friends is nearly drowned by an underwater monster, with endless rows of razor-sharp teeth. No one is quite sure what they saw. Was it a moray eel? A giant barracuda? There's only one thing Emmet knows for certain. Dr. Catalyst is back....