Every Saturday Jim, Mickey and Lisa battle in paintball wars held in the city’s storm-drain system. The new kid, Carter, wants to join their club, the Sewer Rats. Lisa doesn’t want him in the club. She devises risky tests for him and puts him in the path of danger at every opportunity. But the tunnels under the city are dangerous enough on their own, and soon the kids find themselves trapped and terrified as the tunnels fill with water.