A blown operation in Pakistan leads J.T. to work alongside the FBI to find a spy in the E-Ring; J.T. is shocked when Pierce's new boyfriend, Master Sgt. Brian Meeks, is identified as the prime suspect for leaking the classified information. Meanwhile, Col. McNulty is kept out of the loop during J.T.'s investigation. Also, Bobby suspects his wife is having an affair.

In North Korean waters, a submarine that Bobby's team is on collides with a North Korean nuclear submarine, damaging it. The Korean commander is eager for the Americans to save his crew, but he must work against his own countrymen, who have sent another vessel to kill everyone aboard rather than allowing the Americans to get their hands on the Korean submarine.