The Man Who Was No. 16 is the culminating contest between the Beresfords and a master of disguise whose methods expose the danger behind their detective role-playing. Mr. Carter’s warning prepares Tommy and Tuppence for the visitor, and Tommy correctly identifies him through the prescribed password; yet the agent’s apparent capture proves to be a trap, and Tuppence is abducted from the hotel under the eyes of the watchers meant to protect her.

Warning and Preparation

The danger is introduced by Mr. Carter, who tells Tommy that a special agent has been sent from Moscow. The man’s identity and arrival details are unknown, but Carter describes an adversary who caused trouble during the war, is Russian by birth, speaks enough languages to pass as several nationalities, and is exceptionally skilled at disguise. He is also the inventor of the No. 16 code. Carter expects him to approach the agency under the pretext of a case and test its occupants with passwords. The Beresfords are advised to answer correctly, sustain the fiction, and remain alert even if the visitor seems deceived.

Carter’s warning makes the agency itself a monitored point of contact. He has arranged for a dictaphone to be installed in the office, with an agent in the room below listening to conversations. The surveillance is meant both to protect Tommy and Tuppence and to help secure the man Carter wants. It places the visitor within an official net, but also establishes the central problem of the episode: the adversary understands disguise and performance well enough to turn observation into another vulnerability.

The Beresfords meet the threat through the same imaginative method they have used in their work: adopting detective-fiction roles. Tommy recalls the supposed return of the criminal No. 4, whom he claims to have defeated in the Dolomites with explosives, and recasts the new enemy as No. 16, or No. 4 squared. He takes the role of Hercule Poirot, while Tuppence answers as his friend Hastings. Their exchange turns the approaching danger into a familiar game of character parts and detective conventions; beneath the comedy, however, they are preparing to test a real visitor against a real code.

The Password Test

A buzzer sounds, and Albert brings Tommy a card bearing the name Prince Vladiroffsky. The visitor enters as a graceful, fair-bearded man who appears to be about thirty-five. Tommy and Tuppence receive him in character, allowing the meeting to proceed as a test rather than confronting him outright.

The stranger first asks whether the agency has branches across the Channel. Tommy answers with the second password, stating that he himself was in Berlin on the thirteenth of the previous month. The visitor then drops the pretense: he says the daughter of his friend can be dismissed and acknowledges that the Beresfords have been warned of his arrival, indicating the calendar on the wall. The exchange confirms that Tommy has passed the test and that the visitor knows they were expecting him. For a moment, the code appears to have done exactly what it was designed to do: identify the agent and establish a basis for dealing with him.

The Hotel Surveillance

Tommy contacts Mr. Carter, who reports that the Prince and the young woman accompanying him are having lunch in the restaurant. Carter has two men posing as waiters among the diners, men watching the visitor’s suite upstairs, and others stationed outside to follow the pair. Tuppence, too, is to be kept under observation. The plan depends on continuous coverage: the visitor may be deceived, Carter believes, but the agents will be ready if he moves.

As the Prince and the girl leave the restaurant, Carter anticipates that the man will take her to his suite. He and Tommy withdraw behind a pillar, while the surveillance continues through quiet reports from men in ordinary roles, including a waiter and a fashionably dressed young man. When the pair go upstairs, Carter’s watchers move to act. Reinforced by two additional men, they enter the suite with a key. The door opens noiselessly; inside are a small hall, an open bathroom, a sitting room, and a closed bedroom door. From behind that door comes a faint sound, which leads Carter into the bedroom.

There he finds a middle-aged, fashionably dressed woman bound hand and foot on an ornate double bed, her mouth gagged and her face contorted with pain and anger. The discovery reveals the violence concealed behind the orderly hotel operation, but it does not yet disclose where Tuppence is. The watchers have entered the suite successfully; the crucial failure is that the man and the girl they were tracking are no longer there.

The Disguise and Abduction

Tommy searches beneath the sofa and pulls out a small rolled bundle. Its outer layer is the long black coat Tuppence wore that day; within it are her walking dress, her hat, and a long fair beard. The discarded clothing turns the apparent movements of the Prince and girl into a carefully staged substitution. Tommy concludes that the Russian has escaped with Tuppence, while the supposed hospital nurse and invalid boy who had stayed at the hotel were accomplices, present long enough for the staff to become accustomed to them.

Tommy reconstructs the likely mechanics of the escape. The agent must have realized at lunch that the hotel was closing in, then taken advantage of the empty room next door, which he had prepared by fixing its bolts. He silenced the woman found in the bedroom and Tuppence, brought Tuppence into his room, dressed her as a boy, changed his own appearance, and walked out in the guise of a nurse accompanying an invalid. The old garments were hidden beneath the sofa, ready to be discarded once the substitution was complete. The scene makes the episode’s governing tactic concrete: clothes and familiar occupations become instruments for managing what witnesses think they see.

Carter identifies the means used to incapacitate Tuppence when he picks up a shining fragment of a hypodermic needle from the carpet. She has been drugged, not persuaded to cooperate. The revelation answers Tommy’s uncertainty about her apparent acquiescence while confirming how thoroughly the agent has controlled the situation. What looked like a watched departure was in fact a change of identities carried out inside the watchers’ blind spot.

Consequence and Significance

Carter immediately rejects Tommy’s fear that the agent has got clear, pointing out that every exit is watched. Tommy sees the weakness in that assurance: the surveillance is looking for a man and a girl, not for a hospital nurse and an invalid boy. Inquiry confirms that the nurse and patient left by taxi about five minutes earlier. The detail exposes the difference between watching a person and watching for an identity; the agents guarded the exits, but the fugitives passed through by appearing to be someone else.

The episode sharply reverses the Beresfords’ comic rehearsal of famous detectives. Tommy can name and recognize the adversary, and the password works, yet neither recognition nor official surveillance prevents the abduction. The encounter therefore shifts from a playful contest in detective styles to a rescue problem with Tuppence’s freedom at stake. The agent’s greatest advantage is not invisibility but the ability to make a conspicuous exit look ordinary: a nurse and an invalid boy are legible to the hotel staff precisely because they seem to require no attention.