Barely five minutes after landing, David senses tension and suspicion in the air. Who are the mysterious men in the airport? What do they want? Does it have anything to do with the diamond mine Mr. Daring is surveying for the government?

The intrigue and tension pick up when the boys stage a daring rescue in the hills to thwart the kidnapping of a mining engineer. Then someone taps the phones. Confidential reports disappear. The three teens face a roadblock in the bush, and someone tries to kidnap them.

David Curtis and Mark and Penny Daring know they'll have to keep their wits about them if they're going to throw their pursuers off track. A heart-stopping chase down a crocodile-infested African river brings David and his friends to a final test of courage and strength as they strive to outwit the mysterious Hoffman and his gang.