“Lindsay?” It was Helen’s familiar voice, Liverpudlian crossed with Glaswegian, untouched by anything south of the M62. “How’re you doing, girl?”

“Off my head with jet lag, but otherwise okay. Listen, Helen, I need a bed a few nights sooner than we anticipated.”

“What do you mean, jet lag? Are you here in London already?”

“Yes. Just me. I’ll explain when I see you, it’s too complicated over the phone. Is your spare room free?”

“Course it is. The whole house is a total tip, though, on account of I wasn’t expecting the pair of you till next week, but if you don’t mind a bit of chaos and no milk in the fridge, move on in. Sophie’ll go nutso when she sees the state of the place, but I’ve had more important things on my mind than tidying and Kirsten wouldn’t notice if the council started emptying bins into the living room, bless her,” Helen gabbled.

“Sophie’s not with me,” Lindsay cut in as soon as Helen paused for breath.

“Aw, Lindsay, you’ve not done one, have you? I know you, first sign of trouble and you’re off over the horizon. You should stay and talk it over, you know you should. You’re a million times better for her than I ever was.”

Lindsay laughed. “Give me some credit. I have grown up a wee bit in the last half-dozen years. There’s nothing wrong between me and Sophie, I swear. The reason I’m here early is something else entirely. Look, I’ll explain when I see you, okay? I’m running out of money here.”

“All right. Listen, can you get yourself round to the office? Only I’ve got to leg it to an important meeting, but I can leave the spare set of keys with reception, and you can sort yourself out, is that okay?”

“That’s fi–” The money ran out and Lindsay found herself talking to dead air. She hailed the first cab that passed and asked him to wait outside the warehouse in Camden occupied by Watergaw Films while she picked up the keys. They stopped at Meredith’s to collect Lindsay’s luggage, then carried on to Helen’s terraced house in Fulham. As the black taxi juddered through the early afternoon traffic, Lindsay pondered her next move. Collecting keys and luggage had reminded her that she needed to check out the flat where Penny had been living.

Dredging her memory for details of a half-forgotten dinner conversation with Penny and Meredith, Lindsay recalled that Penny had swapped her house for a flat in Islington belonging to a friend of Sophie. An academic, Lindsay recalled. A philosopher? A psychologist? A philologist? Something like that. The Rubik’s cube of memory clicked another turn and the pieces fell into place. A palaeontologist attached to the Natural History Museum. Called . . . She pinched the bridge of her nose in an attempt to awaken her protesting brain as the taxi rattled along Fulham Road. They turned into a side street wide enough for cars to double park without obstructing the road, then rounded the corner into a street of three-storey terraced villas, their stucco in varying states of repair that reflected whether they were single residences or split into rented flats. As the taxi squealed to a halt, Lindsay suddenly realized she didn’t really need to remember his name. He was the man living in Penny’s house, at the end of a phone whose number she knew almost as well as her own.