The drama follows Alison Wilson who thinks she is a normal, happily married woman. But when her husband Alec suddenly dies, a woman turns up on her doorstep, claiming that she is the real Mrs Wilson. Alison is determined to prove the validity of her own marriage - and Alec's love for her - but is instead led into a world of dark and troubling secrets. Alec was a British spy and a best-selling novelist and Alison is pushed to the very brink to find out the truth.