The Agatha Christie Hour: The Red Signal (1982)

After prominent psychiatrist Sir Alington West is shot in his home, suspicion falls on his nephew and heir Dermot West. Earlier that evening they had both been a séance hosted by Jack and Claire Trent. The only message the medium had for them was not to go home. Sir Alington invited his nephew in for a nightcap and subsequently revealed that he was at the Trents in a professional capacity. He has concluded that Claire Trent is severely disturbed and needs to be put away. Dermot is quite in love with the woman and threatens his uncle within hearing distance of Sir Alington's manservant. The police find the murder weapon in Dermot's home but he sets off into the fog-bound night to find his uncle's killer.