Spandrin was a Lemuran who was sent by the Sinestrans to kill Trenix for the sake of the Syndicate. To do this, he killed and possessed Jimmy Lynch and influenced Hugo and Kathy Blake for six months in order to use their gang to take out his target.
As Jimmy, Spandrin tracked Trenix down to Reynolds Hardware and was thwarted in his attempt to kill him by the Fourth Doctor and Ann Kelso. When the sight of Trenix's true form broke down the gang's conditioning, Spandrin killed them and summoned Sinestrans to take over their corpses. The group attacked the police station where Trenix was being kept and he eventually took over Trenix's body, after which the Sinestrans killed him in order to get their own bodies back from the Doctor. (AUDIO: The Sinestran Kill)