The Return by Michael Gruber Henry Holt, $28.00, 366 pages, ISBN 978-0-8050-9129-8 Have you ever had dark fantasies?  You know the kind—the ones where you plot a scheme to get even with someone, or something.  Then, reality hits, you come to your senses and the daydream ends with thoughts of the consequences of those actions and the fears of getting caught. But . . . what if . .