Cambridge, 1866
The master of Jesus College has been loosing his memory for some time, and his wife has been running the college. She is exposed when the body of one her students is found on the banks of the Cam. Scotland Yard is called in, and Inspector Leslie and Sergeant Pashtine arrive from London.
They find the student was a member of a secret university society which apes the Hell-Fire clubs of old. They expose bad behaviour and corruption extending as far as the Master's own daughter. But the odd, inward looking college life and its eccentric members take their toll on Leslie, and he is distracted for some time from the true culprits.

Leslie also manages to fall out with a local police inspector, who he discovers is involved with local thieves and a culture of thieving along the river running through the colleges. It is this clash of cultures, between town and gown, which finally offers a solution to the mystery, if Leslie can avoid being taken off the case in disgrace.