Gemma Doyle is excited about celebrating Jayne Wilson's big day. It's supposed to be a day marking not only the birthday of Jayne, her partner in crime, but also that of the Great Detective himself. Following the festivities at the Sherlock Holmes Bookshop and Emporium, Gemma heads for the Blue Water Cafe, the site of Jayne's party. To make things even better, Jayne's wedding is only a week away. But the much-anticipated affair quickly turns to disaster with the presence of the bride and groom's respective exes in attendance and other unruly guests. With drama at every corner, Gemma and Jayne take a break on the chilly deck overlooking the ocean when they spot the body of a party attendee floating in the water below. As Detective Ryan Ashburton takes a closer look at the guest list, Jayne's wedding is in peril, especially when it is revealed that her fiance, Andy, is a prime suspect. With the police closing in and more lives on the line, it's up to Gemma to keep Andy from prison and save Jayne's wedding day from ruin.