For their new assignment, Sapphire and Steel arrive at an abandoned railway station haunted by supernatural figures. Paranormal investigator George Tully has been observing the station for several weeks because he has an interest in speaking with the ghost of a young man often heard whistling in the hallways. Sapphire and Steel indulge Mr. Tully by allowing him to help their investigation but Steel warns him that the apparition is something far more dangerous than a ghost.