Who committed the murder in book and then there were none?

The murderer in Agatha Christie's *And Then There Were None* is U.N. Owen, revealed to be the alias of Judge Lawrence Wargrave.

He is the mastermind behind the entire scheme, meticulously planning and executing the killings of the eight guests on Soldier Island. He does this as a form of twisted justice, believing the guests are all guilty of crimes they have committed and gone unpunished by the legal system.