The story:
The Phantom (as Mr. Walker) is travelling on a cruise ship when the alarm bell is sounded: most passengers' cabins have been looted during a well-attended dinner dance. A shipwide search is started immediately, beginning with Mr. Walker's cabin. To the latter's amazement, a gem from the loot is found during the search.

Chased by the ship's authorities, the Phantom is in a tight spot with little room for manoeuvre and has to find the rest of the loot and those responsible before the trail goes cold...