The Van Der Byl diamond company, willed by bequest to the founder's son, Benedict, his sister Tracey and their estranged foster-brother Johnny Lance, turns out to be a bequest not of love, but of hatred. For it is couched in such terms as to offer Benedict the instruction to 'destroy Johnny', something he is only too willing to do. Tracey sets out to support Johnny, and acquires for him the concession in the diamond-rich seabed round the coral islands off the coast of South West Africa. Johnny is sure that he will repair his fortunes at last. But Benedict, already involved in illegal diamond-dealing, seizes his chance to attack, and with a network of accomplices and some ingenious tampering, plots to syphon off the diamonds. Johnny can only be ruined by his liabilities, but it turns out that Benedict's obsessive greed and jealousy is his undoing...