noun. A ghostly double of a living person, especially one that haunts such a person.

noun. An evil twin.

noun. A remarkably similar double.

noun. A person who has the same name as another.

noun. A fantastic monster that takes the forms of people, usually after killing them.

"A few minutes later the real Lance arrives at the nightclub to the amazement of Stone and Dina; he explains his doppelganger is his older brother former army intelligence specialist Barton, who still suffers from an amnesia causing blow to the head."

doppelgänger