The FBI asks Charlie to retrace the path of a marine salvage barge because Don suspects a murder took place on board. However, Charlie is put in a difficult situation when the National Security Agency (NSA) also requests his help to find the yacht for the confidential case they are working on. Meanwhile, Liz and Don try to figure out a way to make their personal relationship work after she is permanently transferred to LA.
Meanwhile, Alan and Millie's relationship continues to develop. Millie prepares to challenge Alan at chess.