Sam (Jared Padalecki) and Dean (Jensen Ackles) investigate the mysterious deaths of several men who apparently dropped dead of fright. They visit one of the victims in the morgue, and Dean becomes infected with the illness which starts as a general anxiety, then moves on to full-blown terror that eventually stops the heart.

Sam and Bobby (Jim Beaver) must find the root of the disease before Dean dies and is sent back to Hell.