U. N. Owen (Mr. Owen)

U. N. Owen is revealed to be Justice Lawrence Wargrave, a retired judge who created the alias — a spoken pun on "unknown" — to lure ten individuals guilty of unpunished murders to Soldier Island and kill them one by one. The truth is disclosed through a confession letter retrieved from the sea after all ten guests have died, making Owen the novel's central enigma and its most carefully concealed presence.

Owen sends invitations under false names such as "Mr. and Mrs. Owen" and "Una Nancy Owen," enlisting his agent Isaac Morris to purchase the island and manage the arrangements. Each guest receives a plausible, personalised reason to visit, ensuring none suspect a trap. Morris is then poisoned before the island events begin, eliminating the one person who could identify the real mastermind.

Owen manipulates Armstrong more than any other guest, first accusing him of performing a botched operation while drunk, then flattering his professional vanity to recruit him as a secret accomplice in faking Wargrave's death. Once Armstrong has served his purpose and becomes the only person who knows the "corpse" is a ruse, Owen drowns him — demonstrating that collaboration with Owen is a death sentence.

Owen's stated motive is a warped judicial logic: each victim committed a genuine homicide that the law could not punish, so he appoints himself as judge, jury, and executioner. His posthumous confession letter concedes a darker layer — a lifelong sadistic "lust to kill" that he claims to have suppressed during his respectable career and finally allows to merge with his sense of judicial authority on Soldier Island.

Owen secretly recruits Dr. Armstrong to stage a shooting, after which Wargrave's "corpse" is laid out with theatrical solemnity among the remaining guests. This removes him from the list of suspects while he continues killing. He later drowns Armstrong to silence the only witness to the ruse, leaving no one alive who can expose the deception before his confession letter is found.

Owen never physically interacts with Vera; instead, he constructs a psychological trap — the gramophone accusation, the diminishing ceramic soldier count, the "Ten Little Soldiers" nursery rhyme hung in every bedroom — that erodes her sanity over days. His final move is leaving a noose in her room with a chair positioned beneath it. The accumulated dread he engineered drives her to hang herself, fulfilling the rhyme's last verse entirely through his victim's own hands.

Owen uses the rhyme as both a sentencing document and a strict programme for the killings, framing it in every bedroom so the guests watch their own deaths foretold in verse. Each murder mirrors the rhyme's sequence, with a ceramic soldier toppled to mark each death. His strict adherence to its order suggests a need for ritual — justice rendered with the procedural precision of a formal verdict.

Owen's identity is revealed through a posthumous confession letter sealed in a bottle and retrieved from the sea after all ten people on Soldier Island are dead. The letter is Wargrave's self-authored summation, delivered to what he calls a nonexistent courtroom. Because the only account of his identity and motive is written by the killer himself, with no living witnesses to corroborate or challenge it, Christie leaves the reader in the unsettling position of accepting a murderer's word as the final truth.