A Treacherous Bastard - Tammy Andresen

No one would mistake him for a hero.

Though Lord John Foxcroft has been the heir of the Earl of Marlborough since birth, his family has always known the truth. He's a bastard, a fact his father has never let him forget. So it was only natural that he became a spy. Why not keep secrets for a living?
But when his game of cat and mouse with a criminal mastermind catches an innocent debutante in the crossfire, he must choose. Save the girl or catch his man.

The choice ought to be simple.