Zaddik by David Rosenbaum
Recently divorced, spiritually adrift, and recovering from alcoholism, Dov Taylor, an ex-cop from the NYPD, is called upon to recover one of the world's greatest treasures: the Seer's Stone, a magnificent 72-carat diamond. The gem was to be used as dowry in a historic wedding meant to unite two powerful, bitterly antagonistic Hasidic sects, but has been removed from the sanctum of New York City's diamond center and placed in the hands of the Magician, a Nazi collaborator and notorious war criminal. In a difficult quest of recovery, Taylor forges a link through time and solicits the help of his exalted ancestor, Hirsh Leib of Orlik-- a zaddik and prince of Israel from 19th-century Poland, a country ravaged by war and fanaticism. To succeed, Taylor must commit his very life to a law older and more awesome than any on the books.