Tumult — John Harris Dunning

Adam Whistler has it all, so why does he feel so empty? When he breaks his ankle on a Mediterranean holiday he impulsively ends his relationship, toppling himself into emotional free fall.
 
At a house party he meets -- and beds -- the lovely Morgan. But when he encounters her a few days later she has no memory of him and introduces herself as Leila. Leila has dissociative identity disorder, or multiple personalities.
 
People are being murdered and Leila fears that Morgan, the personality Adam first met, is the killer. He doesn't believe that any part of her is capable of it, so he sets out to unravel the mystery of her past. Tumult is a stylish, contemporary psychological thriller in the vein of Alfred Hitchcock and Patricia Highsmith.