Keating paused for breath and she took the opportunity to ask the question that had been troubling her from the start of the investigation. ‘I don’t understand,’ she said, ‘how nobody noticed. A Metro packed with people. She’d have screamed, wouldn’t she? Joe didn’t hear her, but he was at the other end of the carriage. There would have been blood.’

‘No,’ Keating said. ‘There was hardly any blood. Not enough for anyone to notice.’ With the aid of an assistant he rolled Margaret onto her side. ‘She was stabbed by a knife with a very thin blade. Long and thin. She’d have felt it, but more as a discomfort than any real pain. A pin prick. Then, if the subcutaneous fat closed over the wound, there would have been hardly any external bleeding. She’d have died before she or anyone else realized what was happening.’

Vera wondered if that was a good way to die. Just before Christmas on a busy train, surrounded by excited bairns and adults full of beer. She could think of worse ways to go.

‘So he knew what he was doing?’ she said. ‘The murderer, I mean.’

Keating shrugged. ‘Either that or he was lucky.’

‘She was stabbed from behind?’ Vera couldn’t see how that would work. The woman was sitting down. Joe had described in detail how she’d taken the one empty seat in the carriage. So how could she have been stabbed in the back?

‘Definitely from behind.’

He continued to make his report, but Vera was running that image over and over in her head. Margaret, well dressed, stepping from the snowy platform into the train, finding a seat and leaning back against it. Vera created scenarios to explain the knife wound in the back, the sharp blade piercing the cashmere coat. Perhaps Margaret was being followed from Gosforth and was stabbed while she was still standing. But if that was the case, why had the killer waited to make his attack until she was in a crowded train? A dark and quiet suburban street would surely provide a better opportunity. Or perhaps Margaret had turned in her seat to look out of the window as the train pulled into a station and the killer had taken a chance then. In either case the murderer could have left the train at any stop between Gosforth and Partington. They’d assumed that Margaret had been killed close to the final stop, but if death had crept up as unobtrusively as Keating had suggested, that needn’t have been the case.

Keating’s words had been running as a background to her thoughts and she noticed a sudden silence.

‘What is it?’ She was jerked back to the present, to the freezing mortuary and the stink of human waste.

‘Our victim was ill.’ Keating stood for a moment, frowning. ‘Bowel cancer. I found these indications on the liver. The disease had spread from the bowel.’