Moonlighting S01.E05 Next Stop Murder

O.A.D. March 26, 1985 . "Next Stop Murder"
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The agency's ditzy receptionist, Agnes DiPesto, wins a place on a "murder mystery train" hosted by a famous writer of mystery stories. Maddie and David take her to the station and find themselves trapped on the train as well. While the train is in motion, the writer is murdered and the Blue Moon trio find that every one of the passengers had a motive. The episode concludes with a showdown atop the moving train.