Dagger of the Mind (S02E04)

During a professional trip to London to study British policing methods, Columbo finds himself entangled in the murder of wealthy businessman Roger Haversham, who has been supporting two struggling theater performers. When Haversham threatens to withdraw his support, he is murdered. Shortly after, the butler uncovers the truth behind the murder and begins blackmailing the actors. In a desperate move, they kill him and stage it as a suicide out of guilt for Haversham's death. Columbo, however, uncovers their scheme using a pearl and a newly acquired umbrella to bring the culprits to justice.