Judge Wargrave cast his back in his mind to remember when exactly he had last seen Lady Constance Culmington. It must be seven—no, eight years ago. She had been going to Italy to bask in the sun and be at one with nature and the contadini…. Constance Culmington, he reflected to himself, was exactly the sort of woman who would buy an island and surround herself with mystery! Nodding his head in gentle approval of his logic, Mr. Justice Wargrave allowed his head to nod….

The narrator introduces Judge Wargrave while he sits on the train riding toward the island and looking at his invitation, purportedly sent by an old friend. While he seems to be trying to explain to himself the mystery of who owns the island, in fact—readers learn at the end—he created this letter himself and the “logic” of the invitation gives him a plausible cover story for why he, like the other guests, arrives at the island.

Where had he seen that frog-like face, that tortoise-like neck, that hunched up attitude—yes and those pale shrewd little eyes? Of course—old Wargrave. He’d given evidence once before him. Always looked half asleep, but was shrewd as could be when it came to a point of law. Had great power with a jury—it was said he could make their minds up for them any day of the week. He’d got one or two unlikely convictions out of them. A hanging judge, some people said.

Armstrong provides his point of view of Wargrave that reflects a bit of history between the two characters. Armstrong’s impressions paint a portrait of Wargrave as persuasive, strategically subversive, and willing to dispense the ultimate punishment. Readers also get a hint that Wargrave might have convinced a jury to convict unjustly—an idea later supported by the recording the guests hear.

Only Mr. Justice Wargrave and Miss Brent seemed comparatively unmoved…. The judge sat in his habitual pose, his head sunk down into his neck. With one hand he gently scratched his ear. Only his eyes were active, darting round and round the room, puzzled, alert with intelligence.

After the guests listen to a recording accusing each of murder, their reactions vary. Readers note that Wargrave appears unmoved but interested, which could stem from his personality, as one who observes far more than he acts. Or, like Miss Brent, he does not consider himself guilty of any crime. Readers do not understand at this time, however, that Wargrave himself produced the recording.

He’d enjoyed that case! Matthews’ final speech had been first-class. Llewellym, coming after it, had failed to remove the good impression that the defending counsel had made. And then had come his own summing-up…. Carefully, Mr. Justice Wargrave removed his false teeth and dropped them into a glass of water. The shrunken lips fell in. It was a cruel mouth now, cruel and predatory. Hooding his eyes, the judge smiled to himself. He’d cooked Seton’s goose all right!

Wargrave reflects on his crime as exposed by the recording. Wargrave was accused of sending Seton, an innocent man, to his death. Far from feeling culpable, Wargrave seems proud of how he treated Seton. Wargrave will later reveal he believed Seton to be guilty and influenced the jury’s conviction. The narrator’s description of him as a merciless predator intends to cast a spotlight on his sinister judicial actions.

“Now we know exactly where we are.” There was no doubt now who was in charge of the situation. This morning Wargrave had sat huddled in his chair on the terrace refraining from any overt activity. Now he assumed command with the ease born of a long habit of authority. He definitely presided over the court.

Wargrave marks the point at which the guests on the island recognize a sinister plot is unfolding. Macarthur’s death cannot be explained as accidental or suicidal, and that fact alters the survivors’ perceptions. Wargrave takes charge of the discussion about what has been happening, why events occurred, and what they should do. As a retired judge, Wargrave naturally leads this inquiry and the others defer to his authority. His seeming determination to get to the bottom of the mystery allows him to steer the group’s conclusions.

“We come now to the death of General Macarthur. That took place this morning. I will ask anyone who considers that he or she has an alibi to state it in so many words. I myself will state at once that I have no valid alibi…. “I sat on that chair on the terrace for the whole morning until the gong went, but there were, I should imagine, several periods during the morning when I was quite unobserved…. There is only my word for it that I never left the terrace. In the circumstances that is not enough.”

By pointing out that he has no real alibi for Macarthur’s death, Wargrave seems to be arguing that all facts must be accepted, however unpleasant, and that all the guests must be considered suspects—even those who might try to claim innocence based on character or reputation. Such a stance portrays Wargrave’s intellectual rigor and moral straightness. Ironically, Wargrave has no alibi because he did murder Macarthur. His seeming search for justice serves as a smokescreen to deliberately mislead the others.

I must keep my head…I must keep my head…If only I keep my head…It’s all perfectly clear—all worked out. But nobody must suspect. It may do the trick. It must! Which one? That’s the question—which one? I think—yes, I rather think—yes—him.

Five paragraphs of quoted thoughts appear unattributed on the page as the five remaining guests all think about each other with suspicion. Readers do not yet understand that these thoughts in particular belong to Wargrave. This realization occurs to readers only in hindsight as the story wraps up. As he explains here, Wargrave needs to remain calm to continue murdering while not getting caught, and “Which one?” refers not to the perpetrator but to the choice of an accomplice Wargrave can use to help him fake his own death.

I was born with other traits besides my romantic fancy. I have a definite sadistic delight in seeing or causing death. I remember experiments with wasps—with various garden pests… From an early age I knew very strongly the lust to kill. But side by side with this went a contradictory trait—a strong sense of justice. It is abhorrent to me that an innocent person or creature should suffer or die by any act of mine. I have always felt strongly that right should prevail.

In a letter found at sea, Wargrave explains why he committed the murders. Along with a strong sense of justice, he has also always had a strong desire to murder. Although the document serves as a posthumous confession, Wargrave reveals no remorse and intends the document to function as a revelation of his masterpiece. As the “artist” of the mystery, Wargrave wants credit for his work.

For some years past I have been aware of a change within myself, a lessening of control—a desire to act instead of to judge. I have wanted—let me admit it frankly—to commit a murder myself. I recognized this as the desire of the artist to express himself! I was, or could be, an artist in crime! My imagination, sternly checked by the exigencies of my profession, waxed secretly to colossal force.

Wargrave’s lifelong appetite for killing the guilty had been satiated by his career as a judge. In recent years, he explains, secondhand murder no longer felt like enough. Later, Wargrave reveals that he suffers from an incurable illness. The medical death sentence motivates him to undertake the thrill killing he’s wanted all his life.

During all this time of search my plan had been gradually maturing in my mind. It was now complete and the coping stone to it was an interview I had with a doctor in Harley Street. I have mentioned that I underwent an operation. My interview in Harley Street told me that another operation would be useless.… I did not tell my doctor of my decision—that my death should not be a slow and protracted one as it would be in the course of nature…. I would live before I died.

While Wargrave has been planning his murders for a while, his realization that he is dying causes him to finally put his plan into action. He can now commit the murders and then commit suicide, perpetrating the perfect crime. The deaths of nine guilty people who have evaded justice will satisfy his intense, deep-seated craving to kill. Then he can die feeling fulfilled with this capstone to his life’s work.