A Knight in Tarnished Armor by Cynthia Luhrs

Last summer, on what was supposed to be the trip of a lifetime, Amy’s best friend vanished without a trace.

After much pleading, her parents agreed to one final trip to England to search for clues as to what really happened to Lily, and then she’ll come home and get on with her life. But when she’s accused of tampering with the dig and loses her job, not to mention any chance of working in the field ever again, Amy flees and everything goes horribly wrong. Then she meets an unlikely trio of sisters, fellow time travelers, who just might be able to aid her.
Christopher de Savage, the feared Wolf of Wolfshire, has no time for damsels in distress, especially ones that break his nose. He has a castle to repair, enemies knocking at the drawbridge, and somehow has to find a way back into the good graces of his brother.