Shroud for the Archbishop by Peter Tremayne

Wighard, Archbishop designate of Canterbury, has been found dead, garrotted in his chambers in Rome's Lateran Palace in the autumn of A.D. 664. His murderer seems apparent to all, since an Irish religieux was arrested by the palace guards as he fled Wighard's chamber, but the monk denies responsibility for the crime, and the treasures missing from Wighard's chambers are nowhere to be found. The bishop in charge of affairs at the Lateran Palace suspects a political motive and is wary of charging someone without independent evidence. So he asks Sister Fidelma of the Celtic Church to look into Wighard's death. Fidelma (an advocate of the Brehon Court), working with Brother Eadulf of the Roman Church, quickly finds herself with very few clues, too many motives, a trail strewn with bodies--and very little time before the killer strikes again.