Is the solution to this mystery lost at sea? When Captain Sewell is found battered in his cabin aboard the Hakota, Felix Dunn takes command. It emerges that the ?upright? Captain had some diamonds on board ? and they are missing. Suspicion soon falls on Dunn. His estranged wife has been overspending ? and he has been in trouble before. But the attractive DC Helen Ryan believes he is not their man and is prepared to go some way to find out the truth.