Abby Mills returns to Harper's Island for the wedding celebration of her best friend, Henry Dunn, and his bride-to-be, Trish Wellington. Abby hasn't been home in seven years, since her mother and five others were murdered by John Wakefield.

As the wedding party embarks on a scavenger hunt, Trish confronts an old flame, Henry makes peace with some locals and Abby runs into a friend who is haunted by John Wakefield and the island’s tragic past.

When a local girl’s death is ruled a suicide, Abby challenges her father, the Sheriff, to investigate what really happened. As the wedding approaches, Trish must come to a decision about Hunter.

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.

A father/daughter bike ride in the woods leads to a startling revelation. Abby uncovers the Sheriff's secret obsession as Trish and Henry's wedding rehearsal takes an unexpected turn.

With the wedding party reeling after the deadly events at the rehearsal, Abby, Henry and J.D. take matters into their own hands as they try and solve the murder.