To Wed a Scandalous Spy (Royal Four #1)

Lovely, high born Willa Trent was an orphan, raised by a local, somewhat odd family in the country, who want nothing but the best for their girl. So when she drags the unconscious man she accidentally hit with a slingshot home, they arrange a hasty marriage and pack the couple off with best wishes. Armed with a groggy husband and a new future, Willa's pie-eyed optimism has no limits...until she discovers the secret, dangerous world of Nathaniel Stonewell, Earl of Reardon, a.k.a. "Lord Treason."

Though Nathaniel is reviled by most of England for his devious plot against the Crown, he is, in reality, a member of an elite cadre of secret royal defenders on a daring undercover mission. He must keep his secrets at all cost, especially from Willa. And yet, he is enchanted...though he stubbornly refuses to surrender to his passion. Far better, he tells himself, to turn his back on love than risk everything for it. Luckily, his bride has other plans...
Rated '4/5 - Explicit open door' for steam/spice/heat level.