Magnum, P.I. (1980)

It is almost the 4th of July, and Higgins heads to Maui for an annual writers conference, and Rick and T.C. take a trip away, leaving Thomas on the Estate to face the horror of his tax audit. But that's nothing compared to the terror yet to come when Magnum becomes the focus of a crazed, obsessed killer, who repeatedly phones him with cryptic nursery rhyme riddles of upcoming killings. At first he thinks it is a crank caller, but the full reality of the sitution hits home when a prostitute is murdered in circumstances reflecting the clues given, and the menacing calls continue, with the deranged killer boasting about his crimes and giving clues of the next one...