On Christmas Eve, Miriam Caravasios steps onto the ice that surrounds her seaside estate on Maine's Mount Desert Island. Miriam, her mind clouded by dementia, doesn't hear the snap of thin ice until it's too late. Did someone lure the old woman to her death? There are plenty of suspects; Miriam's family has gathered to celebrate Christmas. But it's Delphine, Miriam's granddaughter, who comes in for the greatest scrutiny when they learn that Miriam's will cut off her children, leaving her granddaughter almost everything. As tensions rise, Delphine is emboldened to start asking questions. The trail will take her into the past - and eventually onto thin ice.