A Thief in the Night by KJ Charles

Toby never meant to be a highway robber, but needs must. He didn't plan to impersonate a top London valet either, but when the chance comes to present himself as the earl of Arvon's new gentleman's gentleman, he grabs it. Unfortunately, the earl is the man he seduced and robbed on the road to get here. Oops.

Miles, Lord Arvon, is not impressed. But he's faced with a tumbledown home and lost family fortune, and desperate times call for desperate measures. Toby—shameless, practical, and definitely desperate—may be just the man he needs.

To steal back a priceless bracelet, that is. What else were you thinking?