Wikipedia
Brother Cadfael is the main fictional character in a series of historical murder mysteries written between 1977 and 1994 by the linguist-scholar Edith Pargeter under the name "Ellis Peters". The character of Cadfael himself is a Welsh Benedictine monk living at the Abbey of St Peter and St Paul, in Shrewsbury, western England, in the first half of the 12th century. The historically accurate stories are set between about 1135 and about 1145, during " The Anarchy", the destructive contest for the crown of England between King Stephen and Empress Maud.
As a character, Cadfael "combines the curious mind of a scientist/pharmacist with a knight-errant". He entered the cloister in his forties after being both a soldier and a sailor; this worldly experience gives him an array of talents and skills useful in monastic life. He is a skilled observer of human nature, inquisitive by nature, energetic, a talented herbalist (work he learned in the Holy Lands), and has an innate, although modern, sense of justice and fair-play. Abbots call upon him as a medical examiner, detective, doctor, and diplomat. His worldly knowledge, although useful, gets him in trouble with the more doctrinaire characters of the series, and the seeming contradiction between the secular and the spiritual worlds forms a central and continuing theme of the stories.
Cadfael is the name given to the TV series adapted from The Cadfael Chronicles novels written by Ellis Peters. It was produced by the ITV Central between 1994 and 1998. The series was broadcast on the ITV network in the UK, and starred Derek Jacobi as the medieval detective. They were aired in the US as part of the Mystery! series.