Thank you to NetGalley and Michael Joseph, Penguin Random House for this ARC.

Cam, young mother of baby Polly has her first day back at work after maternity leave. She doesn't know where her husband Luke is and he has only left a cryptic note but she isn't too worried until the police raps at her office door.

The facts as set out to her are that Luke has taken three hostages in a Bermondsey warehouse and he is armed. A siege continues until hostage negotiator Niall comes on the scene and tries to engage Luke. Then he lets the female hostage go, shoots the other two dead and disappears, never to be heard of again. Until, seven years later, Cam receives a cryptic email and begins to try and get answers but each clue throws up more questions.

The story is told in dual POV between Cam and Niall, both traumatised by the events they couldn't stop and that have changed their lives.

The twists and turns are excellent but I have to say that the plot drags in the middle when Cam is blocked at every turn from finding out more. Whatever it is that people are hiding, it must be big. Why did no one ever find out who the hostages were? Was Luke good after all?

We get an insight into Niall's life and the therapy he's been having for PTSD. His wife left him as he always prioritised work, and he has never forgotten that terrible siege so when covert surveillance of Cam suddenly throws something up, he is right back in, and this time he doesn't just want the perpetrator - he wants the truth, unlike his colleagues who just want to close a case at the expense of what really happened.

This is a thriller of course but it's also an exploration of love and relationships and how well we really know someone. It's an engaging read, with Cam's sister and her battle with IVF prominent, as is Cam's work as a literary agent.

As usual, Gillian McAllister delivers in spades. This is an outstanding suspenseful psychological thriller with two unique, believable POVs that go deep into the human psyche.