Monique Sims washes ashore on a life raft. Monique had been on the yacht Serenity. Jerry finds the yacht via satellite, with bodies all over the deck. McGarrett, Danny, Junior and Tani board the yacht, which has 11 dead people on board. McGarrett concludes the people were exposed to a biological agent, and now so has the Five-0 team. McGarrett has Jerry and Grover interview Monique. McGarrett has the team stay on the yacht so they don't risk exposing anyone else. McGarrett grabs a tissue sample to send back with Noelani on the chopper. The hospital lab identifies the bio-weapon as a synthetic chimera virus, for which there is no cure, unless there's already an antidote. Monique recalls the party, and tells of a man named Marko holding a gun on the guests. Monique got on the life raft and escaped. Grover suggests that Marko may still be on the boat. McGarrett finds Marko dead holding a case. The case held the virus, with one ampule busted. Marko had been shot with a flare gun. Marko was in charge of a Ukrainian bio-weapons program. Monique was lying, because she was Marko's accomplice The buyer for the virus calls to threaten Monique. She overcomes a nurse and escapes the hospital. Adam gets the Swiss bank to reveal who wired money to Monique's Cayman Islands account. Five-0 catches the buyer, forcing him to set up a meeting with Monqiue. She runs, and a cop shoots her when she pulls a gun. Grover stops the medics to get Monique to confess where the antidote is. Grover flies out to the yacht in a storm. McGarrett jumps overboard to save the case with the antidote in it. Then Junior jumps in to save him. Tani pulls them both in.