AllMovie

During a Christmas office party, executive Tony Gould (Joseph Cotten) is confronted in his office by his secretary -- and mistress -- Shelley (Chris White). Fed up with being strung along by the married Tony, Shelley threatens to reveal their relationship if he doesn't divorce his wife immediately. In desperation, Tony strikes Shelley down, killing her instantly -- only to discover that he has locked himself in his office, and will be trapped therein for the next three days.