While investigating the murder of a fellow police officer in the British West African colony of Gambia, ex-patriot Inspector Harry Sanders (Richard Todd) discovers links to a sinister diamond smuggling operation working further up the River Gambia. The evidence points to a clinic run by Dr. Schneider (Walter Rilla) and his assistant director, Dr. Weiss (Albert Lieven). At first, Inspector Sanders suspects that a local businessman Jack Pearson is behind the crimes. But when Pearson together with American journalist Jim Hunter are murdered, Sanders realises he was mistaken and begins to suspect that the clinic may be the centre of a diamond smuggling ring. Can the Inspector solve both the murder and the centre of the smuggling activity before the River resonates once more to the funeral beat of the 'Death Drums'?