Helen, a "diamond runner," reaches South Africa. Among her letters of introduction is one to Sir Thomas Holstead. She visits the "business quarters" of the ring of diamond runners of which Paul Hurst is the head. Hurst informs Helen that she can easily gain access to the diamond mines by attending the Holstead reception and becoming acquainted with the Holsteads, who own large mining properties. Helen attends the reception and is received with great favor by Sir Thomas and his son Forty. After a dance with Forty, they repair to the conservatory, followed by Inspector Harrington. Paul dispatches one of his henchmen to convey the message to Helen. The messenger finding Helen, writes Hurst's message on the window in chalk. This is seen by Harrington. Helen makes ready to leave. Forty invites her to visit the mines. Next morning Forty and Helen visit the mines, closely trailed by Harrington. Coming to the place indicated by Hurst's chart, Helen sits down to rest. While Forty busily points out to her different places of interest, she craftily scoops up the diamonds which have been cached under the stone upon which she is sitting. These she puts in her bag, watched all the time by Harrington. Harrington accuses Helen of stealing a number of diamonds. Helen cleverly embeds the diamonds in the hearts of rose buds of a bouquet. Before passing into the chamber to be searched, she hands the bouquet to Forty. He gives Inspector Harrington and the mine manager each a rosebud. Returning from the fruitless search, Helen passes out accompanied by Forty, who sees her to the hotel. Shortly after Harrington discovers the presence of the diamond in the rosebud. Meantime, Helen hastily plucks the stones out of the buds. A number of detectives rush to the hotel. She hears them approach and wraps up the stones and attaches them to a toy balloon which she sends out of her window. After a fruitless search, the detectives leave. Hurst comes in. Harrington follows shortly. In her inner chamber Helen tells Hurst of the balloon. He starts south, locates the balloon and recovers the stones. Hurst arranges for Helen to leave at once for the States, and tells her the package of diamonds will be delivered to her at the dock under the letter "H" in the baggage room. The Holsteads plan to leave on the same vessel. Their maid's name is Helen also. By chance, the maid Helen is under the letter "H" in the baggage room when the messenger approaches, and forces the package into her hand. Inspector Hudson is detailed to sail and scrutinize Helen's actions. He meets Helen through Sir Thomas. Helen, accidentally discovers the package in the maid's trunk. Hudson protects Helen when she is attacked by Hurst. Upon landing, Helen gets into a taxi pre-arranged by Hurst to carry her to their rendezvous, where she is kidnapped and searched. Hudson follows closely with the police, who rescue Helen and capture the band of smugglers.