Cain His Brother — Anne Perry

In his family life, Angus Stonefield had been gentle and loving; in business, a man of probity; and in his relationship with his twin brother, Caleb, a virtual saint. Now Angus is missing, and it appears more than possible that Caleb--a creature long since abandoned to depravity--has murdered him. Hired to find the missing man, William Monk puts himself in his shoes, searching for clues to Angus's fate and his vicious brother's whereabouts. Slowly, Monk inches toward the truth-and also, unwittingly, toward the destruction of his good name and livelihood....