The Scoundrel and the Debutante by Julia London

The dust of the Cabot sisters’ shocking plans to rescue their family from certain ruin may have settled, but Prudence Cabot is left standing in the rubble of scandal. Now regarded as an unsuitable bride, she’s tainted among the ton. Yet this unwilling wallflower is ripe for her own adventure. And when an irresistibly sexy American stranger on a desperate mission enlists her help, she simply can’t deny the temptation.

The fate of Roan Matheson’s family depends on how quickly he can find his runaway sister and persuade her to return to her betrothed. Scouring the rustic English countryside with the sensually wicked Prudence at his side—and in his bed—he’s out of his element. But once Roan has a taste of the sizzling passion that can lead to forever, he must choose between his heart’s obligations and its forbidden desires.