DIA Agent Thomas Park falls on top of a car during a premiere. Sam is living in a trailer on the beach, but isn't ready to go back to work. Deeks hasn't told his mother that he and Kensi are engaged. The team meets their new assistant director, Shay Mosley, who tells them Hetty has retired. She also informs them North Korea is launching a missile at Los Angeles that day. Mosley shakes things up by pairing Callen and Kensi and sending Deeks back to LAPD. Lt. Bates gives him a desk in the canine unit. Nell and Eric try to track Hetty for Callen. Callen and Kensi find video of two men tossing Park off the roof. One of the men is Michael Lee. Callen and Kensi break into his house, with Mosley's permission. Deeks chases his mom's male caller out of the house. She's mad at him because he didn't tell her about his engagement. Lee comes home with another man, who pulls a gun and escapes, after shooting Lee. Callen calls Sam to fill him in on what's been happening. Callen brings Deeks back and gets Mosley to agree to it, for now. Sam also returns. Callen and Sam think Iran is behind the missile rumor, so that North Korea would get blamed for any explosion in LA. Sam hits Deeks with his car, to distract the bomb-maker in the ambulance, then Callen shoots him. The bomb has been activated, so Callen drives the ambulance toward an airport while Sam attempts to defuse it. He can't, and they can't make the airport, so Callen drives into the harbor instead. Mosley dresses down Callen for their "cowboy" way of operating, and he takes it under advisement. Hetty is on an overseas mission, tracking a former American operative.