Carlos Malfeitor is the main antagonist of the horror-movie, Witchboard and was a serial axe-murderer in life - following his death he became an evil spirit that communicated with the world via the Ouija board belonging to Brandon Sinclair.
Malfeitor uses Brandon's girlfriend, Linda, as a pawn and pretends to be a boy named David - taking control of Linda and ultimately using her as a vessel by which to enforce his will upon the living world.
At first Malfeitor (still guised as David) seems pleasant towards Linda but unbeknown to her is that while entertaining her the spirit attacks and kills one of Jim's friends at a construction site - this prompts Brandon's attention as Jim had previously insulted David during a Ouija board session.
Brandon and Jim do research on David and accuse him of terrorizing Linda, however when they play the Ouija board and discover that Malfeitor is the one frightening Linda, the spirit then attacks and kills Brandon.
Released from the hospital (due to her weakened state, caused by Malfeitor's influnce), Linda plays the board but gets no response; she then takes a shower, but gets attacked by Malfeitor. She initially escapes but soon is possessed by the evil entity. The next morning, Jim arrives back and sees the apartment trashed, with Linda appearing—wearing men's formal wear and holding an axe.
Just then, Dewhurst, the detective investigating the murders committed by Malfeitor (and suspecting Jim as the perpetrator), enters the apartment. He accuses Jim of hurting Linda, but finds out in rapid order that he is wrong, when the detective immediately gets smacked on the face by a rod—which renders him unconscious and causes him to drop his gun. Jim picks up the gun and shoots the board many times right before Linda pushes him out the window.
However by shooting the board Jim manages to free Linda from Malfeitor's influence - effectively banishing the evil spirit.
Yet in typical horror-movie fashion the board is soon discovered by an unwitting bypasser, who asks if it still works before tossing it into a box - for the camera to zoom in as the board answers with an ominous "Yes".