A seasoned private detective investigates a violent night raid at a family residence where a valuable collection of diamonds has been stolen and a relative murdered; household members are assaulted or found unconscious while servants report no alarm and puzzling access points suggest a calculated crime. The narrative follows careful inquiry, interviews, and sharp deduction as the investigator traces clues, infiltrates the criminal network responsible for the theft, and combines action with puzzle-solving to unravel motives and recover the stolen gems.