Judson, Theodore. "The Sultan's Emissary"
Divergence: 453 CE
What if: Attila's Huns won the battle at Chalons, but the fractured Europe they left behind was eventually swept up by the Muslim invasion.
Summary: In 1650, an emissary from the Ottoman sultan is murdered in Britain, the last remaining Christian nation.
Published: In Sideways in Crime: An Alternate Mystery Anthology (ed. Lou Anders), q.v.