Dark deeds in the Lighthouse Library threaten to send Lucy Richardson's soon-to-be-wed cousin Josie to an early till-death-do-us-part.

Winter falls on North Carolina's Outer Banks as Lucy Richardson and her friends joyfully help her favorite cousin, Josie O'Malley, plan her wedding. The owner and head baker of Josie's Cozy Bakery and her fiancé, chef Jake Greenblatt, want a small, simple wedding.

But to their horror, Josie's imperious grandmother, Gloria, descends with the "Louisiana Mafia," a gaggle of aunts and cousins who intend to take control of the wedding plans. Gloria doesn't do small and simple, and cousin Mirabelle has her own ideas for Josie's wedding, something grand and lavish―and paid for by Josie's parents, of course―that will kickstart her fledgling event-planning business and get her work shown on the covers of wedding magazines. To make matters worse, Mirabelle focuses her full Southern charm on the prospective groom, and Jake doesn't seem entirely adverse to her attentions.

To smooth the waters, Lucy hosts a bridal shower at the Bodie Island Lighthouse Library. But it turns deadly when Mirabelle collapses―soon after eating the gluten-free treats that Josie prepared specifically for her. Now, to save her favorite cousin from prison, Lucy will have to bring a crook to book.