Monk's Hood is a medieval mystery novel by Ellis Peters, set in December 1138. It is the third novel in The Cadfael Chronicles. It was first published in 1980 (1980 in literature). It was adapted for television in 1994 by Central for ITV. Gervase Bonel dies from monkshood oil put in his food. Brother Cadfael made the oil. Who used it as poison? Cadfael assesses the motives of Bonel’s family and household staff, including his Welsh natural son and his stepson, and deals with Bonel’s widow. She was once his sweetheart, long ago. The sergeant views the case differently from Cadfael.