Ex police officer Socrates Smith and his brother Lexington, who is also an amateur sleuth, are invited to spend a weekend at Peter Mandle's country home. Shortly after they arrive the brothers notice many precautions taken against intruders, a message flashed in Morse code, and someone skulking across the lawn. „Come three oaks", it spells in Morse code. Early next morning the brothers take a stroll, and there, tied to an oak branch, is a body with a purple mark where the bullet struck. A nicely convoluted mystery with plenty of incident, murder, forced marriage, kidnapping and so on from the master of mystery Edgar Wallace.