No two men could have been more opposite in every way than Wilfred and Clarence Cheriton. Wilfred, forever immersed in some engineering experiment, had little use for people and business activities, whereas Clarence was a sociable man with a gift for selling the products of the Cheriton Engineering Works, of which he and his cousins were partners. If only the two cousins could have made allowances for their differences, it was a partnership which should have worked well. But they couldn't, and the sudden death of Wilfred led Inspector James Waghorn of New Scotland Yard to make some very searching inquiries into the affairs of the Cheriton family. Once again, 'Jimmy' Waghorn is helped in his investigations by the enigmatic advice of Dr. Priestley, while Sergeant King's encyclopedic knowledge of the underworld plays its part in the solving of a particularly ingenious crime.