When a marine is shot, the team investigates. They start by talking to him, he tells them that he went riding and he got shot probably by a hunter. They check out his story and learn he wasn't telling the truth. They go back to see him but he left the hospital, not fully healed. They learn a relative came and helped him. They see the relative, who doesn't know much but they find a bag filled with drugs. They think the bag belongs to his son. So they try to talk to him but he disappeared. They think the boy was asked by a drug ring to deliver the drugs but he changed his mind which means his father is trying to protect him. But the gang will stop at nothing to get them, so they try to find them. When Kai's father doesn't see his doctor, Kai needs to put aside his feelings to help his father.

When evidence to put away a drug kingpin is stolen, Lucy goes undercover at an underground poker tournament to find out which high-roller is behind the crime. Also, Lucy’s feelings are in turmoil when Whistler’s ex-girlfriend arrives in town.

Following a close call at a meth lab explosion, the NCIS team learns Kai is being targeted by his old friend-turned-criminal and must take him down; Lucy gets her first big case aboard her aircraft carrier.