One of the most popular episodes of the hit Fox television series, the X-Files, is now available on cassette. When a serial killer strikes a fourth time leaving no trace of how he entered or escaped from the scene of the crime, FBI agents Fox Mulder and Dana Scully are called in to investigate. Soon, all evidence points to the impossible: a murderer who has been squeezing through air ducts and chimneys since 1903. Can Mulder and Scully stop him before he strikes again?