Last of all, caught in the seam at the back of the drawer, was a plain envelope. Freeing and opening it, she pulled out a photograph.

It was of a baby scan, the grey shape of a tiny infant obvious. On the back a name for the child that had never been born, Mac, and the words ‘My son’ in Greg’s handwriting.

It was a discovery too far. Fumbling with the envelope, she tried to make her trembling hands put the picture back. That’s when the other item inside slipped out to fall directly into her lap.

The fine gold chain unfurled itself, the name tag at its centre clear enough to read.

It said Ailsa.

Why did Greg have a necklace that surely belonged to Ailsa Cummings? And why was it in beside a picture of his unborn son?

The reason presented itself almost immediately, and suddenly the hold Caroline appeared to have over Greg seemed obvious.

Ailsa hadn’t been a passing acquaintance, too young for Greg to even take note of. It seemed she may have been much more than that.

Joanne thought again of all the times Greg had lied to her about Ailsa. How often he’d given the impression that he barely knew her. Yet he’d kept a memento of her beside an ultrasound scan of his baby.

Eventually, pulling herself together, she retrieved her weekend case from the corner and began to pack. Whatever evidence the police had on Greg must have pointed to him knowing Ailsa a great deal better than he’d claimed.

Her imagination now working overtime, she conjured up her own version of the story. Ailsa hadn’t been stalking Greg, like Caroline suggested. It had been the other way round. He’d become obsessed with the teenager and, when she’d rejected him, he’d raped and murdered her.

Even as she imagined this, she knew she was turning him into a version of Richard.

She also couldn’t believe that Caroline, if she even suspected such a thing, would have continued to cover for him, including giving him an alibi for that night.

Bundling everything into the case, she went to the bathroom to fetch her toiletries, then remembered the pregnancy test.

Her hand shook as she retrieved it from among Greg’s shaving things. Clasped in her hand, the blue message that life was already growing inside her freaked her even more now than it had before.

She couldn’t have this baby, even though she’d briefly toyed with the idea. A child inherited half its DNA from its father, and whether that father turned out to be Richard or Greg, it was bad news.

Stop it, she told herself. You are the product of your parents, and yet you are nothing like them. In fact, for years you thought you might have been adopted.