At the urgent plea of his old friend, Commander Buchanan of Scotland Yard, Tweed, once ace detective, now Deputy Chief SIS, visits Mrs Bella Main, formidable matriarch controlling the Main Chance, the most powerful private bank in Europe. Bella tells Tweed and Paula Grey, his assistant, that she has refused an enormous offer from Calouste Gubenkian, the most ruthless and villainous man in Europe. Within days of their visit Bella is murdered.

Tweed and Paula return to investigate the atrocious act. The bank's HQ is based in a huge Elizabethan manor hidden in The Forest, a vast area in the deep south of England. Tweed has already met members of the two families, run by their forefathers for generations. Was Bella murdered by one of them - or is it the work of the vicious Calouste?

The movement never stops, changing to Calouste's Chateau Les Rochers in the Belgian Ardennes. A ferocious battle takes place. Two more murders are committed at the manor. Tweed and Paula race to tiny Seacove on the rugged Cornish coast to prevent another murder. Finally, Tweed proves the Bank, founded in 1912, was based on a brutal crime all those years ago.