Benedict (David McCallum) and Tracey Van Der Byl (Hayley Mills) are the offspring of wealthy Hendrich Van Der Byl (Bill McNaught), who owns and operates Van Der Byl Diamond Mines, one of the smaller yet still very lucrative diamond mining operations in South Africa. Benedict and Tracey grew up with Johnny Lance (Jon Cypher), who Hendrich brought into their house when orphaned and has treated him like another son which Benedict has always resented. While Benedict is a ne'er do well who spends his time chasing women, and on the side steals a diamond here and there from the company to give to whomever his female companion at the time, the current being Johnny's gold-digging wife Ruby (Volenté Bertotti), Johnny, who has overshadowed Benedict all of their lives, has learned the business, and is one of the most respected diamond men in the country. With what Johnny believes is a large cache of diamonds sitting within the reef at Thunderbolt Gap which the larger mining operations have the rights, he has developed Kingfisher, a new vessel which he believes will revolutionize the dredging for such diamonds. The bank has loaned the company over two million dollars thus far, with Kingfisher actually being operational within sight. When Hendrich receives a terminal medical diagnosis which he tells no one in his family, he hands over the reigns of the company one-third each to Benedict, Tracey, and Johnny. Benedict assumes the role of President and C.E.O. in Hendrich giving him the chance to prove himself, something that Benedict said he wanted. Tracey's share is held in a trust controlled by Benedict. And Johnny's share is solely within the realm of Kingfisher and the dredging operation, he needing to negotiate further with the bank for any additional capital to complete the vessel and make it operational. While Tracey and Johnny, who have always had a soft spot for each other, decide to go into business together in completing Kingfisher, Benedict, with Ruby by his side, tries to use his control through legal albeit amoral means to take over the entire company, including Kingfisher, with the ultimate goal of ruining Johnny, he not caring if Tracey is collateral damage. As Tracey and Johnny try to overcome anything that Benedict throws in their way, Benedict resorts to more criminal and potentially deadly means to get what he wants. The prize becomes bigger when they collectively discover some information about Thunderbolt.