Thornapple

From Goodreads:

A renegade monk, a scheming lady of the manor, a mysterious old woman, and a beautiful boy guarding magical secrets. These are just some of the intriguing characters encountered by a young pedlar as he journeys through the east of England in 1204. Their stories intertwine to form a fast-moving tale of romance, murder and witchcraft, taking us from Norman castle to Saxon hovel, from the studios of Paris scholars to the dens of London thieves.