He smiled at her genuine anxiety that he would have to pay money he could not afford. He had been intending to ask her to telephone the office of Freddie Bestigui again, and to begin a search through online telephone directories for Rochelle Onifade’s Kilburn-based aunt. Instead he said:

‘OK, we’ll vacate the premises. I was going to check out a place called Vashti this morning, before I meet Bristow. Maybe it’d look more natural if we both went.’

‘Vashti? The boutique?’ said Robin, at once.

‘Yeah. You know it, do you?’

It was Robin’s turn to smile. She had read about it in magazines: it epitomised London glamour to her; a place where fashion editors found items of fabulous clothing to show their readers, pieces that would have cost Robin six months’ salary.

‘I know of it,’ she said.

He took down her trench coat and handed it to her.

‘We’ll pretend you’re my sister, Annabel. You can be helping me pick out a present for my wife.’

‘What’s the death-threat man’s problem?’ asked Robin, as they sat side by side on the Tube. ‘Who is he?’

She had suppressed her curiosity about Jonny Rokeby, and about the dark beauty who had fled Strike’s building on her first day at work, and the camp bed they never mentioned; but she was surely entitled to ask questions about the death threats. It was she, after all, who had so far slit open three pink envelopes, and read the unpleasant and violent outpourings scrawled between gambolling kittens. Strike never even looked at them.

‘He’s called Brian Mathers,’ said Strike. ‘He came to see me last June because he thought his wife was sleeping around. He wanted her followed, so I put her under surveillance for a month. Very ordinary woman: plain, frumpy, bad perm; worked in the accounts department of a big carpet warehouse. Spent her weekdays in a poky little office with three female colleagues, went to bingo every Thursday, did the weekly shop on Fridays at Tesco, and on Saturdays went to the local Rotary Club with her husband.’

‘When did he think she was sleeping around?’ asked Robin.

Their pale reflections were swaying in the opaque black window; drained of colour in the harsh overhead light, Robin looked older, yet ethereal, and Strike craggier, uglier.

‘Thursday nights.’

‘And was she?’

‘No, she really was going to bingo with her friend Maggie, but all four Thursdays that I watched her, she made herself deliberately late home. She drove around a little bit after she’d left Maggie. One night she went into a pub and had a tomato juice on her own, sitting in a corner looking timid. Another night she waited in her car at the end of their street for forty-five minutes before driving around the corner.’

‘Why?’ asked Robin, as the train rattled loudly through a lengthy tunnel.