Spanning over fifty years, Ill Humour follows Dr. Anna Mercer as she struggles to treat a patient named Adam Renfrew, whose sickness makes no sense within the terms of modern medical knowledge. But a chance encounter brings Anna into the company of Donald Firkin, a divorced English professor who soon discovers that Anna's patient makes all too much sense, just not according to modern science. Through a series of manipulations, Firkin convinces Anna that her patient's internal organs have travelled backward through medical history, taking on the properties of the "four humours" of medieval science. What ensues is a sometimes wry, sometimes passionate story of blackmail, family, and romance. And time-travelling organs.