We are a somewhat squeamish Sloth.  So when Before I Go To Sleep opened with an extreme close up of Nicole Kidman’s graphically bloodshot eye, we nearly had to reach for the smelling salts.  

Christine (Nicole Kidman) has lost her memory. Each morning she wakes up in bed next to an apparent stranger who turns out to be her husband, Ben (Colin Firth).  Ben patiently explains to her, as he has done each morning for numerous years, that she is suffering amnesia after an accident. Each day Christine will learn anew about the life she leads until she goes to sleep, at which point her memory is wiped once again.

But in the past two weeks Christine, unknown to Ben, has secretly started treatment with neurologist Dr Nash (Mark Strong).  Keeping a daily video diary at his instruction to aid her memory, she begins to experience flashbacks from her earlier life. Flashbacks that lead her to question whether Ben is being entirely truthful to her.

Before I Go To Sleep is based on the mega-hit, best seling novel. Which naturally raises the question – is it better than the book? Well, no. But how many films are?  Much as The Sloth loves the moo-vies, the nuance and detail of 500-odd written pages are seldom improved by reducing to 90 minutes of screen time. So let’s judge it on its own merits. It might not reach the Hitchcockian-esq heights it clearly aspires to – all claustrophobia and menacing score – but it kept us cheerfully hooked for all of those 90 minutes. Boasting a subversively sinister turn from Colin Firth, and equally confounding Mr Nice Guy turn from rent-a-villan Mark Strong, if you need a servicable little runaround of a thriller, it’s perfectly reliable.

UK release 5 September