Professor de Worms reveals at the end of Chapter 8 that he is actually an actor named Wilkes who was recruited to be a police detective, and not a professor at all. This moment is a twist of situational irony:
The curse of the perfect artist had fallen upon me. I had been too subtle, I had been too true. They thought I really was the great Nihilist professor. I was a healthy-minded young man at the time, and I confess that it was a blow. Before I could fully recover, however, two or three of these admirers ran up to me radiating indignation, and told me that a public insult had been put upon me in the next room. I inquired its nature. It seemed that an impertinent fellow had dressed himself up as a preposterous parody of myself.
As Wilkes recounts his origin story, he reveals that there is another, real Professor de Worms whose identity has become his own, following an impersonation he made of the man for mere hilarity’s sake. Despite simply playacting, his skills at deception are so convincing that Wilkes is ironically mistaken for the Professor, while the true de Worms is accused of fraud. Now, both the real and fake Professors de Worms must live out lives they did not anticipate:
The real professor was thrown out, but not with violence, though one man tried very patiently to pull off his nose. He is now, I believe, received everywhere in Europe as a delightful impostor. His apparent earnestness and anger, you see, make him all the more entertaining.
The very definition of what constitutes one’s identity comes into question in this scene—Wilkes has been living as the Professor for so long he has effectively become him. This case of mistaken identity brings the novel’s discussion of truth, falsehood, and disguise even more clearly to the fore for the reader to examine.
In Chapter 12, the Secretary attempts to arrest Syme for breaking the law, thus revealing himself to be yet another policeman and not a devoted member of the anarchist movement. This is a moment of both situational irony and dramatic irony, as the Secretary does not know that the man he is attempting to arrest is in fact a would-be ally, another police officer (while the reader and Syme know the full picture):
“There is some mistake,” he said. “Mr. Syme, I hardly think you understand your position. I arrest you in the name of the law.”
“Of the law?” said Syme, and dropped his stick.
“Certainly!” said the secretary. “I am a detective from Scotland Yard,” and he took a small blue card from his pocket.
“And what do you suppose we are?” asked the professor, and threw up his arms.
“You,” said the secretary stiffly, “are, as I know for a fact, members of the Supreme Anarchist Council. Disguised as one of you, I—”
The certainty with which the Secretary asserts that Syme is a member of the Supreme Anarchist Council is equal to the hilarity of the scene when he discovers, only a moment later, that none of the council members are actually anarchists at all. Chesterton uses irony in these revelations to invoke larger considerations of identity and faith. Each time the detectives encounter another undercover ally, they are forced to question everything they know thus far regarding the rebellious anarchists they aim to subvert. With every test of their resolve and determination, the detectives, and Syme in particular, are brought closer to their faith.
