‘Go to Bessie immediately; you will be safe there,’ reads the farewell letter that Sonja finds in her father’s home after it has been robbed. Prominent inventor Lucius Lindner has taken his own life to escape ‘The Black Ravens’, a gang of which he was once a member himself. He leaves Sonja the secret formula for his excelsior rays, an invention which the criminal gang is eager to get their hands on. Sonja follows her father’s advice to seek out safe lodgings with her friend in the big city. Unfortunately, the Black Ravens, whose leader is known as the ‘Queen of Clubs’, are ahead of her and kidnap Sonja at the main train station. Can Bessie, who is a female detective, rescue Sonja from the gang’s clutches?