Highlander: The Raven S01E03 - Bloodlines

While on a security detail, Nick prevents the assassination of a politician. He is forced to shoot the would-be killer, who then falls to his death from atop a building, but when the assassin's body disappears, Nick suspects that he is an immortal. He asks for Amanda's help in tracking him down, but Amanda is hesitant to assist him, as she was friends with the immortal, Morgan Kenworth, in a past life. In flashback to 1897 New York, the son of Kenworth is murdered while he is speaking at a union rally.