Scarecrow and Mrs. King (1983)

S2E12 Ship of Spies

Amanda and Lee take on the roles of a married couple during a cruise to locate a missing informant of Lee's, who was investigating a significant lead. The twist is that upon reaching a remote island, they are required to tie the knot. Once they arrive and exchange vows, they discover a plot involving silver smuggling taking place on the ship. The smugglers, desperate to protect their illicit fortune, will stop at nothing, even resorting to murder, to eliminate Amanda and Lee.