Letter from the dead (1946)

Architect Poul Friis Henriksen falls in love with Norwegian Gerd. Unfortunately, she is already engaged to the doctor Arne Lorentzen, whose former wife died of an overdose under mysterious circumstances. Gerd invites Poul to a party at her home, where he accidentally sees her secretly taking a syringe. This makes Poul suspect that Arne is anything but the perfect husband. He sets out to investigate the matter further.