With an unmanned, half-mile-long freight train barreling toward a city, a veteran engineer and a young conductor race against the clock to prevent a catastrophe.

Ellen Brody still lives in the island resort town of Amity, and her sons Sean and Michael don t work at Sea World anymore, and some time ago, Ellen s husband Martin Brody died of a heart attack that happened because he was afraid of sharks. Sean is now a deputy in Amity. One night, during the Christmas season, Sean is called to untangle a log from a buoy, and when Sean goes to the buoy, he s killed by a great white shark. After hearing about this, Michael, who is studying to be a marine biologist, visits Amity with his wife Carla and his 5-year-old daughter Thea. Wanting to get away from Amity and spend Christmas with Michael, Carla, and Thea, Ellen goes with them to their house in the Bahamas on an airplane whose pilot is Hoagie Newcombe, and Hoagie starts falling for Ellen. Michael s friend Jake, who is also studying to be a marine biologist, lives next door to Michael...

Martin Brody is the new police chief of Amity, an island resort town somewhere in New England. He has a wife named Ellen, and two sons named Michael and Sean. On a Summer morning, Brody is called to the beach, where the mangled body of Summer vacationer Chrissie Watkins has washed ashore. The medical examiner tells Brody that it could have been a shark that killed Watkins. Mayor Larry Vaughn, who is desperate to not lose the money that will be brought in by 4th of July tourists, wants Brody to say Watkins s death was caused by a motorboat propeller instead of a shark, because the thought of a shark in Amity s waters would drive tourists away from Amity. It looks like Vaughn is a mayor who puts money ahead of people s lives. Shark expert Matt Hooper believes Watkins was killed by a shark. Hooper is proven right a few days later, when Alex Kintner is killed by the shark that killed Watkins...