Plot

Princess Mapuana pays Paladin to keep safe a gift - a signet ring from her royal family to our president. But someone is killing off those involved.

Paladin, interrupted from dinner in his room (314) by a noise at the door, finds upon investigating: a knife embedded in his doorframe and a beautiful woman lying senseless in the corridor. When he awakens her, she identifies herself as Princess Mapuana (which he verifies by referring to a book on his shelf) and says that she has a ring that she must convey from her royal family to the King President of the United States. Although she begs him to hold the ring for her, Paladin is skeptical of her story and refuses. Unaccountably, she leaves the ring behind when she departs.

Paladin next receives Prince Kimo, whom the princess has said is her step brother and is trying to take the ring away from her. The prince demands the ring at knifepoint, but Paladin foils him. The prince offers to guide Paladin to someone who can explain things, but as he passes out the door, takes a fatal dart in his back.

Paladin, casting about for a likely perpetrator, confronts the gentleman in room 310, who claims to have been in bed asleep, but who nonetheless has his shoes on his feet.

The next to interrupt Paladin's dinner is Prince Alexei Romanov, who also demands the ring, but is content with Paladin's refusal. He is followed by Professor Jurgen von Hengst, who demands the ring at sword point, but is also foiled by Paladin. After his departure, he too is dispatched by dart.

Paladin decides to lay a trap for the mysterious dart murderer by taking a meal in the hotel dining room, deserted at this late hour. He receives first Princess Mapuana and then Prince Alexei, the latter walking in just as the murderer takes a shot at Paladin, only to be killed by Paladin's handy derringer: it is the gentleman in room 310! Paladin, going through the dead man's pocketbook, discovers passports from Chosen, Russia, Hungary, and Germany.

Alexei and Mapuana discover a mutual attraction and go off to experience Paris. Paladin is left to deliver the ring to the King President.