The Red Monk of Roha

This is inspired by actual events.

Betrayed and left for dead, a soldier in 13th century East Africa winds up in hiding as a monk in Roha (Lalibela). He soon gets romantically entangled with a wealthy heiress as he struggles to maintain his monastic vows. However, when old enemies re-surface and threaten those he has come to care for, he secretly picks up the sword again, offering salvation by day with the Bible, but secretly exacting deadly vengeance and justice by night with the sword.