Jim, Mickey, and Lisa belong to a secret club called the Sewer Rats. Every Saturday, the Sewer Rats reign supreme in paintball wars held in the city's storm drain system. The new kid, Carter, wants to join, but Lisa doesn't want him in the club. When Carter is hurt in his first paintball war, Jim and Mickey suspect that Lisa planned the accident. They try to confront her, but she runs into the tunnels just as a rainstorm begins. Jim and Mickey have to get Lisa out before the tunnels fill with water.