Suspend disbelief in this thriller

Few films demand that viewers make such a herculean attempt to suspend disbelief than Nicole Kidman's Before I Go to Sleep, a would-be Hitchcockian thriller about a woman unable to retain any memories for the last 20 years.

It's a lot to ask of fans. But we'd comply gladly if the film paid off. Sadly, writer-director Rowan Joffé's does not.

Adapted from S.J. Watson's 2011 novel, Before I Go to Sleep features Kidman as a 40-year-old woman who wakes up each morning having lost the memory of half her life. She forgets she's been married for 14 years, that she had a son, that she had a disastrous affair with an abusive lout.

This is hardly a new conceit: Christopher Nolan's 2000 brain-twister Memento starred Guy Pearce as a man with a similar malady. The earlier film rigorously stuck within the logical confines of its premise. Joffé's is filled with far too many contradictions and implausible situations.

We meet Kidman's character, Christine Lucas, on a typical morning: She awakens next to a strange man in a strange bed. The man gets up, each morning, and gently reminds her that he's her husband, Ben (Colin Firth). He sits her down and shows her their wedding photos and describes the car crash that damaged her brain.

Then Ben goes to work while she sits around and broods.

Christine has lived this way every day for 20 years? Really? Who does that?

For one thing, one wonders why it never occurred to her to keep notes, or a diary to jog her memory.

Firth is brilliant as a preternaturally patient man - every day he has to tell her the same exact story. But he has a creepy way about him. Is it love that drives him, or something darker?

Kidman's world is shaken once more when she gets a call from Dr. Nasch (Mark Strong), a specialist who says he has been treating her for weeks. He tells her she wasn't in a car crash but lost her memory after she was nearly beaten to death by a man. And he warns her not to trust Ben.

Dr. Nasch comes up with a startling, original idea: Christine should keep a video diary. Perhaps it could help her recall the attack. She does, by and by, regain bits of the truth. It's a terrifying truth. A truth that could lead to her murder.

Kidman has become too comfortable playing winsome scaredy-cats, a role she perfected in The Others. She's utterly helpless here, and eventually, rather annoying.

Before I Go to Sleep has a few moments of excitement. At one point, it shifts gears into a cat-and-mouse thriller. But it loses steam and falls flat in the third act.