When a rattlesnake at the beach bites a cat, the Critter Gitters are called into action. Upon arriving at the scene, they meet up with Captain Ron, a harbor patrolman who tells the kids of the tragic death of hundreds of sea lions on San Miguel Island. Intrigued by this and eager to help in any way they can, Jimmy and Nick decide to ride out to the island with Captain Ron, where they eventually meet up with a friendly park ranger, who explains to them that it isn't always possible to save every animal. Meanwhile, back at the clinic, Annie stays up all night with the injured cat, doing the best she can to save its life. After a stern warning from the new school principal, Ms. McCracken, it becomes a race against time for the Critter Gitters to get back from the island before they are suspended.