A giant crab interrupts a volleyball game at the Crystal Cove beach, taking the players hostage. This reflects badly on the game’s sponsors, Trickle’s Triquid. Fred constructs a trap for the crab, but it fails, and the crab takes Daphne. The gang then discovers a system of tunnels and catwalks under the beach, which the crab uses to get around. The gang traps the crab, revealing it to be the water company’s mascot, Bud Shelton, who came up with the Triquid formula which Trickle stole and took credit for. Meanwhile, Mr. E sends the gang a newspaper article about four kids who disappeared in the caves, which Daphne uses to identify the kids in the locket photo.