The Red Seal (1920) is a detective novel by Natalie Sumner Lincoln. A man was caught in a 'burglary' in a luxurious house of a rich colonel, who has two beautiful twin daughters. The man is recognized as the burglar at the police court, but then he drops dead. The first diagnose of the cause of death by a non-medical person is angina pectoris. But then they find out that the man was disguised, was the fiancé of one of the twins, the burglary was a wager, according to one of the twins the man was sacrificing himself for someone else, the death could be caused by something else than angina pectoris, and the twins are not always honest with their father…