A habitual criminal named John Amber, a well-educated and charming man with numerous convictions, is released from prison and almost immediately becomes entangled in a complex affair involving two dangerous men, Alphonse Lambaire and his pale accomplice Whitey. After rescuing a young man named Francis Sutton from a crooked gambling club called the Whistlers, Amber meets Francis's sister Cynthia and learns that their late father, a celebrated African explorer, had discovered a fabled diamond-bearing river known as the River of Stars. Lambaire, who had originally financed the elder Sutton's expedition, is now attempting to exploit the discovery, having equipped the expedition with a deliberately falsified compass intended to ensure that no one else could retrace the explorer's route without his proprietary instrument. Lambaire, desperate to rescue a fraudulently floated diamond mining company from collapse, manipulates Francis into joining a new expedition to Africa, ostensibly to verify the location of the mine. Cynthia distrusts Lambaire entirely, but her brother dismisses her concerns, partly swayed by Lambaire's theatrical displays of wealth and generosity. Amber, who is in fact a covert government inspector of prisons operating under the name Captain Ambrose Grey, is simultaneously working with Scotland Yard's Chief Inspector Fell, to whom he delivers forged banknote plates stolen from Lambaire's office safe. He exposes Lambaire as a forger, coiner, and fraudster, though his revelations fall on deaf ears with the credulous Francis. Cynthia secures a Home Office order allowing her to visit Amber in prison, where he has been briefly returned under the brutal governance of a sadistic prison captain. The visit enables Amber to resume his true official identity and be formally transferred from prison service to the Colonial Office's authority. The Colonial Office has determined that the location marked on the elder Sutton's chart points to a barren plateau rather than any diamond field, and that the River of Stars may lie in Portuguese rather than British territory. With Cynthia insisting on accompanying him, Amber sails for West Africa. Meanwhile, Francis has gone ahead with Lambaire and Whitey, and the expedition fails entirely to locate the mine, wandering lost through hostile forest territories. Francis, who refuses to participate in Lambaire's scheme to fabricate evidence of a discovery and defraud shareholders, falls dangerously ill with fever. Lambaire and Whitey, calculating that his moral objections make him a fatal liability, abandon him in the bush and leave him to die. They travel onward reporting his death from fever, carrying uncut diamonds whose origin they cannot explain. Arriving at the coast station where Commissioner Sanders operates, Amber and Cynthia learn that Francis is reported dead. Amber detains Lambaire and Whitey pending the return of a search party sent back to verify their account. The search party finds no grave and no body, but recovers Francis's knotted handkerchief containing several small stones, which Amber identifies as diamonds. In fact, the elder Sutton, whom everyone had long believed dead, had never left Africa. Having discovered the River of Stars during his original expedition, he had remained in the forest in a confused mental state, surviving in a cave beside the dry riverbed where the diamonds lay. When Lambaire and Whitey abandoned Francis, the old explorer found and nursed his son back to health. Both father and son had been concealed in the forest for months, the elder Sutton gathering diamonds and clinging obsessively to the site of his discovery. Amber, refusing to accept Francis's death without proof, remains behind to search while Cynthia returns to England. He eventually finds both men alive, locating them by tracking a leopard shot in the night and following the dry riverbed to a concealed cave. Father and son are brought back to the coast and then to England. Back in London, Lambaire and Whitey, emboldened by the diamonds they cannot account for, float a new and more elaborate fraudulent company, the River of Stars Limited, backed by the diamonds as supposed evidence of discovery and aided by press sensation. Faced with pressure from the Colonial Office to formally locate their claimed mine, and aware that Amber has registered a competing, legitimate company based on the real discovery, they attempt to preempt him by stealing his geographic information and claiming it as their own prior identification of the site. Whitey employs a petty criminal named Coals and conducts covert surveillance on Amber's associates, including the endearingly romantic Peter Musk, Amber's devoted old friend, who inadvertently reveals the location where the Suttons are recuperating in Kent. The elder Sutton, though mentally fragile and locked in obsessive recollection of his discovery, slowly improves in the calm domestic setting arranged by Cynthia and animated by Peter's inexhaustible supply of adventure stories. The resolution of the conflict between the legitimate and fraudulent companies draws near as the Colonial Office presses for a definitive location of the River of Stars, and Amber moves to expose Lambaire's scheme once and for all.
By Edgar Wallace · First published 1913 · Genre: Mystery, Crime Fiction, Thriller · 20 chapters