Close to the end of Trinity Term, 1358, the colleges of the University at Cambridge are at war over the creation of a Common Library. At a meeting of the masters to discuss the matter, a book thrown in the heat of debate strikes on of their number and leaves him seriously wounded. Matthew Bartholomew is called upon for his skills as a physician, but his experience is even more in demand when a body is found floating in the pond of the library's garden--and he is also investigating three murders in the town, the victims rumoured to be targets of a force of dangerous smugglers lying low in the Fens. Working alongside Sheriff Tulyet and Brother Michael, Bartholomew knows he has to disentangle the threads of violence which link academic to trademan--and catch a killer. To fail might mean the destruction of the whole town.