As Wada moved cautiously through the rooms, she was alert for tiny flexions of the boards beneath her feet. She didn’t want Joan hearing any creaks overhead. But she’d always been light on her feet. She remembered how impressed Hiko had been by her ability to walk across the famous nightingale floors at Nijo-jo in Kyoto without making a noise. There weren’t going to be any creaks.

The lounge told her nothing, beyond confirmation, by the positioning of a single armchair directly in front of the television, that Caldwell lived alone. The kitchen was neither manically clean nor conspicuously dirty. A rear door led from there out on to the fire escape. A wall calendar next to the door had the word DENTIST and a time – 10 a.m. – written on the line for the following day. But it had been crossed out. There was no rubbish in the pedal bin. It looked as if Caldwell had expected to be away for several days at least.

Some herbs were growing in pots on the windowsill: basil, coriander, oregano. The earth in the pots felt moist. Wada guessed watering them was something Joan did in Caldwell’s absence. Turning away from them, she caught a sudden reflection of movement in the glass door of the oven, but, wheeling round, she saw nothing beyond the window except trees and sky. A bird in flight, she concluded – nothing to be alarmed about.

Next stop was the study, furnished with desk, computer, landline phone, bookcases, a two-drawer filing cabinet and a stack of cardboard boxes in one corner, with papers piled on top.

Wada clicked the mouse, but the computer didn’t respond. It had been switched off at the wall: another sign Caldwell didn’t expect his visit to London to be a day trip. The desk drawer contained nothing but stationery: pens, envelopes, paper clips, a stapler, a calculator. She tried to open the top drawer of the filing cabinet, but it was locked and there was no sign of the key.

A small red light was flashing on a button on the phone. Message waiting. Wada pressed it and the monitor button.

You have one new message. First new message received today at nine twenty-nine hours.

‘Marty, this is Miranda. Nick Miller tells me you never showed up for your appointment with him. Are you all right? I’ll help if I can, you know. Give me a call when you get this.’

Miranda? Nick Miller? Friends, presumably. The display gave her Miranda’s number, which she recorded on her phone. Then, as she switched off the monitor, she noticed a peel-off jotting pad standing beside Caldwell’s phone. A telephone number was written on the top sheet in pencil, starting with two zeros. She peeled off the sheet and put it in her pocket.