Conan and Rachel are invited to Serena's family beach house. Serena's sister has a fiancé with a family beach house next door, and the fiancé plans to introduce his bride-to-be to his father and brothers that weekend. But plans go awry when Conan witnesses the fiancé killing his father! It turns out the suspected murderer is one of three identical triplets! Can Conan figure out who the real murderer is?