Delia Donovan is the decoy and works for a pair of jewel thieves. Her job is to seduce Viktor, who has in his possession a necklace of priceless emeralds, which he is bringing from Turkey to Marseille for his father. The criminals plan to steal the jewels on the boat with the collaboration of the crooked captain. Viktor's girl friend Sybil sees through the devious Delia and when there is an explosion on board and much confusion, she is the one to come to Viktor's rescue.