The pair go on vacation to Tahiti. The cruise back looks like it will be wonderful, but wouldn't you know it, folks start dying!! It's an odd case, as they hallucinate and end up killing themselves or others--as if they are having a bad acid trip. What is the culprit? Well, you'll have to watch both part one and part two to know the answer to this one.
Part one consists of the folks preparing for the cruise, going on the cruise and the beginning of the carnage. Quincy, not surprisingly, is asked by the Captain to perform autopsies but they are inconclusive, as there really isn't the equipment he needs for a full analysis of the victims. So, samples are helicoptered to Los Angeles where they can do the blood work. When the nearest ports deny them entry, the episode ends with two dummies jumping off the ship and swimming ashore. All in all a good but amazingly familiar episode of "Quincy" that looks a bit like a "Love Boat" crossover since the boat is a Princess ship (though I am not sure if it's the Pacific Princess or just another of their craft.
By the way, in most "Quincy" episodes, despite the seriousness of the plots, there usually is a bit of humor. In this one, it involves Quincy's sex drive. He and his lady friend have separate rooms and Quincy tries, in vain, to maneuver her into sharing a room. She, however, wants nothing to do with this and Quincy's excuses and machinations become sillier and sillier as the show progresses. A bit risqué for 1981!