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 solve the mystery, William Monk puts himself in Angus's shoes, searching for clues to the missing man'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.