Cardassian agent surgically disguised as the Starfleet officer Raymond Boone, used to frame Miles O'Brien for stealing warheads.
Raymond Boone is introduced in Tribunal as an old Starfleet crewmate of Miles O'Brien who served with him at the battle of Setlik III. He chats with O'Brien on Deep Space Nine just before the O'Briens leave on vacation, and O'Brien is soon arrested by the Cardassians.
The crew learns that the real Boone was captured at Setlik III and died in captivity. The man they find is a Cardassian surgically altered to look like him, sent to steal warheads and implicate O'Brien. Sisko brings him to O'Brien's trial, and the court releases the chief.