Gillard sighed and made his way to the surveillance suite in the forensic unit. Near the back there was the wave of an arm from DC Carrie Macintosh, like a schoolgirl trying to attract the teacher’s attention.

‘Sir, I’ve got her. She got off at Earlsfield, the stop before Clapham Junction. Come and have a look.’

Gillard looked over her shoulder and watched the young woman leaving the train. The timestamp on the CCTV said 16.37. Beatrice made her way along the island platform, and down a flight of stairs towards the exit. ‘I’ve got her coming out through the barriers onto the street, too, if you’d like to see that?’

‘Fantastic work, Rainy,’ he said. ‘There’s only one problem. Two minutes later, someone else who was still on the train sent a text from her phone to say she was arriving at Clapham Junction.’

‘Och, she’s a wee witch and no mistake. Vanishes into thin air one minute, but later manages to be in two places at once. I wonder what else she can do?’

When Gillard got home, just before ten p.m., Sam was on the phone but blew him a kiss. She wordlessly guided him back into the kitchen, and indicated to him the moussaka leftovers which just needed reheating. She was clearly in listening mode to one of her large circle of female friends. The exclamations of excitement and approval she interjected as she wandered around with the cordless were an intriguing little detective puzzle in their own right. Gillard often tried to figure out who his wife was talking to based on her tone of voice and the subject matter. To her parents it would be matter-of-fact, flat tones, interspersed with eye-rolling for his benefit. Her mother’s health issues generated the most extreme of these reactions. By contrast her closest friends merited a glass of wine, sips alternating with chuckles and squeals of delight, while she sprawled on the settee, snuggling down for a long session.

This was different. The tone was more surprised, more formal, yet still gushing. ‘No! Really? Oh that’s wonderful. Did he?’ Gillard gave her a mute query, and she mouthed a reply. He didn’t recognise the name. Helen, was it or Ellen? Summoned by the microwave ping, he waved his fingers and blew her a kiss as he retreated back into the kitchen. He left Sam and her friend to their own devices for the next half an hour, suddenly feeling overworked and friendless, eating alone, staring at the oven whose digital clock announced that there were less than ten hours before he had to return to work.

‘So sorry, Craig,’ Sam said, while her husband was stacking the dishwasher. ‘That was Ellen.’

‘Do I know her?’

‘You met her once, at Georgia’s party a couple of years ago. Big glasses, big hips, a bit loud?’

Gillard nodded, though he could only vaguely recall the woman.

‘She’s met a new man, who sounds amazing, and she is utterly in love. She’s dropped two dress sizes. She has always struggled with her weight.’