Tag is an on-campus game that is a fun, thrilling game of assassination using toy guns with suction-tipped darts. Many students participate. Unfortunately, unstable student Gersh becomes obsessed with the game to the point where he actually begins to kill his intended targets with a real gun.
His final target is Susan (Linda Hamilton). Gersh (Bruce Abbott) chases her up several stories of a campus building all the way to the rooftop. As he looks for her on the roof, reporter Alex Marsh (Robert Carradine) comes across a campus cop whom Gersh had just killed. Marsh takes the dead cop's pistol and gives chase up the stairs to help Susan.
Just when Gersh is about to shoot her, a panicked Susan suddenly pulls out her toy gun and shoots Gersh with the harmless dart. She claims victory based on the rules of the game. At first he falls for this tactic, but then he collects his wits when he sees there is no blood, Gersh realizes he isn't dead or hurt.
He points his gun at Susan to finish her off, but then Marsh arrives and tries to shoot Gersh with the campus cop's gun. All it does is go click, click, click. No bullets? Gersh starts to laugh and claims invincibility. But then Marsh's gun finally goes off, shooting Gersh for real. Gersh sees his own blood, says "Well, that's not fair," and then falls to his death to the ground below.