The Sons of Satan — John Creasey

Mallen passes through Customs after a transatlantic crossing, but then a mysterious box that he has smuggled ashore becomes the subject of violent attempts to seize it. Behind these is to be found Abba, an arch-evil buccaneer who will stop at nothing. He is extremely rich and he and his followers will do everything possible to promote international discord and trouble, not least through the practice of black magic. Dr. Palfrey steps into the fray and must somehow deal with the situation before it gets totally out of hand, but that is not as easy as might be imagined.