Mannix is hired by a bank to search for Paul Gantry, an Australian sailor who stands to inherit a sizable sum of money. To find him, Mannix goes under cover at the waterfront posing as a sailor looking for any of his "shipmates" from a recently sunken freighter, the Harlequin, on which Gantry served as one of the crew. As Mannix learns more information about the case, however, he comes to have doubts about whether Gantry really stands to collect the inheritance as his client informed him.
—aldanoli