Magnum, P.I. (1980)

Magnum and a group of his treasure hunting friends are held at gun-point on a cliff-top with the one million dollar prize that was the hidden object of a treasure hunt competition, organised to help promote Robin Masters' new novel by using clues from it. Thomas recounts how they winded up in this predicament: he had been hired by the woman overseeing the treasure hunt to protect her throughout the contest, after it seems that someone is prepared to go to any extent, even to kill, to win the prize money...