Shadows in the Night — Jane Finnis

Roman Britain in 91 AD is a troublesome part of the mighty Empire ruled by Domitian Caesar. Tension is especially high in the north, where Aurelia Marcella, a young innkeeper from Italy, runs the Oak Tree Mansion on the road to York. A string of savage murders disrupts her peaceful life, and she and her Roman friends find themselves under attack from a secret native war-band, the Shadow-men, whose aim is to expel all Romans out. A traveler, Quintus, is nearly killed close to the inn. Soon he and Aurelia team up to track down the rebel warriors and identify their mysterious masked leader, the Shadow of Death.

Reread the beginning of the Aurelia Marcella Mystery series starting with this, the first book (previously published as Get Out or Die).