TC flies out to a freighter at sea during the night to smuggle a Marine deserter back to the U.S.
T.C. makes a late-night flight to land on a tanker, but on the journey back he is cornered and arrested by the Coast Guard for transporting drugs. Magnum and Rick are certain of their friend's innocence, but are shocked when he intends to accept the charges and refuses their help. Magnum investigates to find that T.C.'s trip to the tanker was to collect and bring home a man who once saved T.C.'s life in Vietnam, a deserter who is now a supposedly a reformed drug addict, and who was calling in an old debt to be flown back into U.S. territory.
- Tom Selleck as Thomas Sullivan Magnum IV
- John Hillerman as Jonathan Quayle Higgins III
- Roger E. Mosley as Theodore "T.C." Calvin
- Larry Manetti as Rick Wright
- Jeff MacKay as Lieutenant McReynolds
- Vincent Caristi as Joey Santino
- Charles Lucia as Coast Guard Lieutenant (credited as Chip Lucia)
- Andre Philippe as Renard
- James Hildenbrand as Radioman
- Michael Dennis as Helmsman
- Neal Lipe as Coast Guard Pilot
- Michael Spilotro as Federal Marshal
- Kit Wennerstein as Coast Guard Radioman (as Kit Wennersten)
- Frank Adolfi as Auctioneer
- This was the first episode, after the initial two part pilot, to feature the infamous Magnum, P.I. theme music.
- Starting this episode, different opening credits are used, using Mike Post and Pete Carpenter's familiar theme tune (already heard on the closing credits for the previous few episodes) on the opening credits. This theme would be used, in several versions, for the rest of the show's run.
- The title comes from the German proverb that is translated: Blood is thicker than water.
- Magnum: Sometimes I get so lucky, even I don`t believe it.
- Magnum: Can you give me her name?
- Higgins: Not with you hovering over me like some bloody angel of death.