The Ex — John Lutz

David and Molly Jones, urban professionals, live happily with their toddler son Michael on Manhattan's Upper West Side. Then Diedre Grocci moves into their apartment building. She's David's moody ex-wife, and she wants him back.
Slowly, Diedre lures David back into a world of addictive, violent sex. David is hers for keeps now - or so she thinks. But she doesn't reckon on David's wife. To hold on to her family, her sanity and her life, Molly will go to hell and back.