What happened to Briony in the last 133 hours?

Briony has no recollection of where she's been, or what has happened. Has she been ill or had a breakdown - or could she have been drugged and abducted?

Doubting her sanity, Briony is fearful of what lies beyond the surface, yet driven to discover the truth. Going through her scarce memories, she realizes that something terrible might have happened to her.

Assisted by her friends Alesha and Jenny, they team up with a retired detective to uncover the truth. But where was she for 133 hours... and why?