On their way to Long Island for their wedding weekend, Robin and Barney come across a startling family discovery. Meanwhile, Marshall sees something online that changes the course of his entire journey back east, and Lily confronts Ted about letting go of Robin.

When Lily discovers Ted's list of things he wants to do in New York before he moves for Chicago, she becomes frustrated that she is the only person who knows about his plans. Meanwhile, Robin and Barney realize they have very little time together before their relatives arrive for their wedding.