Don learns that Brian is going to ask Sam to marry him and realises that he still has feelings for Sam. Eddie suggests that Don sees a therapist where he ends up taking the therapist into his confidence and confessing his feelings for Sam, as well as some slightly shocking habits. Sam decides to throw a fancy dress party to celebrate Brian's birthday. Don feels unnerved when he learns that his therapist has come along in fancy dress. Don tries to find him at the party to stop him from revealing any of his secrets. (thetvdb.com)