The second killer and who survived Harper’s Island is revealed as the series concludes. Everything is revealed and three last victims are claimed as four survivors escape from the island.
After witnessing the death of her father, Abby and the rest of the group head out to kill Wakefield. Meanwhile, Shea and Madison find out that one of people they know has a criminal record, and Chloe goes missing when searching for Cal. Five people’s lives are taken by Wakefield, four of them are killed and another commits suicide.
An attempt to leave the island after Katherine has been killed turns into a disaster that will keep the remaining members of the wedding trapped for now. Meanwhile they find out a secret that will leave them reeling, and four more victims are claimed.
The remaining members of the wedding party begin to turn on one another. Then, after discovering the island’s underground tunnel system, they all join together to search for Madison. Two more victims are claimed, but Madison is found alive.
With Madison gone missing, Abby, Henry, Trish, Chloe, Cal, Jimmy, Sully, Shea, Katherine, Danny, Beth and Maggie stay behind to look for her, missing their chance to get off the island. Meanwhile, Sheriff Mills meets an old friend from the past, J.D. escapes from jail, and three more deaths occur.
After Henry, Abby and J.D. try to solve the murders, people lead to think that J.D. is the killer before people are set to leave Harper’s Island, but when the people just finish packing, a horrific mystery will need to be solved, or everyone will be stuck on the island.
The groomsmen take Henry fishing for his bachelor party and make a gruesome discovery. The bridesmaids celebrate Trish’s final days as a bachelorette with a psychic who has a very strong reaction to Abby.