Ellen Brody, the widow of famed police chief Martin Brody, now lives in Amity Island, where her youngest son, Sean Brody, has taken up his father's mantle as a police deputy. Tragedy strikes when Sean is killed by a great white shark while on duty. Devastated by the loss and haunted by nightmares, Ellen becomes convinced that the shark is seeking revenge on her family. Her elder son, Michael Brody, who works as a marine biologist in the Bahamas, insists that her fears are unfounded and invites her to spend Christmas with him and his family to help her overcome her trauma.

While in the Bahamas, Ellen tries to find solace with her son Michael, his wife, Carla, and their daughter, Thea. However, the tranquility is short-lived as strange events start to unfold in the Caribbean waters. Michael and his colleague, Jake, conduct oceanographic research, during which their paths cross with a deadly great white shark. Ellen's suspicions resurface as she believes the menace has followed them to their new haven. While she grapples with her dread, Michael and Jake work against time, trying to protect their loved ones from what seems to be an insatiable predator. Ellen must confront her deepest fears and find a way to protect her family from imminent danger.