"Thank you," I say sweetly when she tells me I'm lucky to have such a beautiful family. But I want to tell her it's not just luck. A family is like a fortress you have to defend all the time. You can't relax because there's always someone looking for a breach, always someone trying to get in. Someone just like her...

When I arrive unannounced at my husband's studio in need of a shoulder to cry on after hearing that my best student, Alex, has died, I see a pair of wineglasses drying by the sink and my deepest fear is confirmed: my husband is having an affair.

Most women would fall to their knees in tears and throw him out of the house-but I just can't bring myself to do it.

Instead, I go home and cook a healthy dinner for our children, walk the dog and unload the dishwasher without complaint. I will make him see that I'm still the woman he married; attractive, successful, the glue that holds our perfect family together. I need this marriage to work to protect a terrible secret of my own, something that would destroy everything I've already sacrificed so much for.

But when the police arrive at my door asking questions about Alex's death that I can't answer, and threatening text messages start appearing on my phone, I know that someone close has been watching me very carefully.

The truth is, there are three people in my marriage, but only one of them is deadly...

An absolutely gripping psychological thriller with a twist that will knock you sideways, perfect for anyone left hungry for more after The Girl on the Train, The Wife Between Us or The Other Wife.

'Wow just wow Nail-biting and suspenseful in the best way possible What a ride ... I devoured this book in one sitting... I could feel my adrenaline surging through my veins the closer I got to the end. I was having palpitations with every twist ' Mrs Leifs, 5 stars