Blow Hot, Blow Cold (1969)

A quirky, but happily in love young Italian couple fall in with an older, but distinctly reserved Swedish couple whilst on vacation on islands off the coast of Southern Italy. Eventually the couples seem to warm to each other as the infectious youths bring the standoffish couple out of their shells. But there is a sinister reason for the Swedish couple's cold behavior and it may spell doom for them all.

Unfortunately the movie Blow Hot, Blow Cold is not yet available on HBO Max.