The team is called in when John Reagan, an off-duty diplomatic agent, is fatally shot. His wife thinks it might be related to his last assignment in Croatia because the shooter had an accent. Reagan's supervisor, Agent Morales, is elusive. The suspect's motel room is rigged with a grenade booby trap. A Croatian testament cross was found in the hotel room. One of the suspects, Luca Cilic, was fired recently from a local lab. A synthetic virus was stolen from the lab. Surveillance shows that Jim Leavins, a researcher, stole the virus he had been working on, a super strain of Covid, and its vaccine. Morales opens up off the record. Reagan was a spy and Cilic is a member of a religious terrorist group. Maggie and OA tail Leavins, who leaves the backpack in a trash can. OA arrests him. But Cilic gets to the backpack before Maggie and opens fires on the boardwalk while running and escapes. Cilic abducted Leavins' wife to get him to steal the virus and the vaccine. Ian figures out where she's being held but she's gone by the time Scola and Tiffany get there. Isobel tries to bluff Leavins to get intel on Cilic. But he wants to talk to her by phone. Isobel orders Ian to cobble together a deep fake of Leavins' wife and he buys it. Scola finds Leavins' wife's body. Based on what litttle Leavins knew about Cilic, Isobel projects that he's headed for Canada. The team corners Cilic but he takes four hostages in a gallery. Maggie attempts to negotiate with Cilic. He wants a jet or he'll release the virus. OA and the tactical squad go in. OA shoots and kills Cilic. Scola retrieves the virus. Isobel has to break it to Leavins that his wife is dead.