The film is set in 1968 in Cu Chi, Vietnam. A new group of US soldiers arrives at the local military camp to assist the troops, called Tunnel Rats, in the tunnel fights. They are told that they would be sent into the first tunnel the very next day. In the tunnels they encounter Viet Cong soldiers, mines and other traps and in the course of the film all the protagonists are killed in firefights, booby traps, bombardments and collapsed or flooded tunnels.