Slightly Sinful by Mary Balogh

As the fires of war raged around him, Lord Alleyne Bedwyn was thrown from his horse and left for dead – only to awaken in the bedchamber of a ladies’ brothel. Suddenly the dark, handsome diplomat has no memory of who he is or how he got there – yet of one thing he is certain: The angel who nurses him back to health is the woman he vows to make his own.

But like him, Rachel York is not who she seems. A lovely young woman caught up in a desperate circumstance, she must devise a scheme to regain her stolen fortune. The dashing soldier she rescued from near death could be her savior in disguise. There is just one condition: She must pose as his wife – a masquerade that will embroil them in a sinful scandal, where a man and a woman court impropriety with each daring step…with every taboo kiss that can turn passionate strangers into the truest of lovers.