The morning after Thomas's sleepover it becomes apparent that Diane has multiple personalities when "Deirdre" emerges and disparages Diane as weak and naive, while describing herself as strong and sexy. In the end, Diane becomes too distraught to live and commits suicide.
- Tom Selleck as Thomas Sullivan Magnum IV
- John Hillerman as Jonathan Quayle Higgins III/Fr. Paddy McGuinness
- Roger E. Mosley as Theodore "T.C." Calvin
- Larry Manetti as Rick Wright
- Deborah Pratt as Gloria
- Gillian Dobb as Agatha Chumley
- Carolyn Seymour as Elizabeth, Lady Ashley
- Sharon Stone as Diane Dupres / Deirdre Dupres
- June Chadwick as English Flight Attendant
- George Innes as David Billingsworth
- Magnum is seen, once again, eating Fig Newtons dipped in milk.
- T.C. is seen wearing a gray "Grambling State Univ." t-shirt, with the number "58" on it. Grambling State is T.C.'s alma mater.
- In exchange for a favor, Magnum gives Rick his two Lionel Richie "best seats in the house" concert tickets.
- Diane (points gun at Magnum): Sorry darling. You really are wonderful, but survival... is survival.
- Magnum: Don't let her kill me Diane.
- Diane: Run Thomas, run!
- Magnum: I can't Diane....Diane, Diedre's dead.
- (Diane shoots the lamp next to Magnum)
- Diane: How's that for dead!?
- Magnum: She's dead. You don't need her to survive.
- Diane: Liar!!
- Magnum: Isn't that what the doctor's told you? You don't need Diedre to survive.
- Diane: She can't live without me! I'm the strong one! I've always been the strong one!
- Magnum: No...Diane's the strong one. She's the one who lived.
- Diane: No! (Fires another shot)
- Magnum: Diedre's dead Diane. You can live without her.
- Diane: No, I can't. I can't control her. She'll come back, maybe not for years, but she'll come back and when she does, she'll kill you!
- Magnum: No, you can get her out of your life forever. We can do it together. I love you.
- Diane: I love you.
- (Diane cocks gun and points it at her head)
- Magnum: Nooooo!!!
- (Diane kills herself)