The scene opens on an ocean liner as it returns to New York harbor, when a woman in a cabin is bitten. Her silent cabin mate just watches her die from the venom. Later in Mr Keen’s office, the sister of the dead woman tells all she knows.

The dead woman, her sister, was breaking it off with a boyfriend who took it badly and began stalking her. To get away, she took the cruise to Europe. The sister went to meet the dead woman in England, and cruise back with her. While in England, she also met up with her new boyfriend, and all took the cruise home together.

Though her stalking boyfriend was on his best behavior on ship, there was an altercation near the end. Evidence seems to indicate thatthe boyfriend knew about snakes, and how to handle them. The sister is forthcoming with a ton of evidence, almost too much if you ask me.

Mr Keen agrees to investigate, and try to find the missing boyfriend. Mike Clancey and Mr Keen are at least smart enough to know that it just as well could be a jealous sister as a jealous boyfriend. Mr Keen and Mike go to talk to the distraught current boyfriend, when suddenly the former boyfriend, Frank, enters in a rage and kills the new boyfriend. Or at least tries to if not for Mike Clancey interfering.

Frank isn’t painting a nice pictre of himself, but when Mr Keen suggests that he turn himself in, I think he may already be forming doubts. A news paper is delivered to announce that a homocidal maniac who killed two people in London is being sought after. Audio keeps cutting in and out through these middle parts, and to the end.

Mr Keen learns more about the character of Frank, and goes to see what he can find out about that aledged maniac. Frank agrees to sit behind bars, but Mr Keen plays his hunch and keeps investigating. He stumbles on some information and orchestrates a trap to force the real killers temper to flare up.

When the drama reaches it’s highest, Mr Keen springs from his hiding place in the closet, and exposes all the details as he puts the finger on the killer.