She waited. Julie had slipped a packet of cigarettes into the pocket of her jacket before she’d left the hotel and she lit one now to pass the time.

It started to spit with rain, so she joined the bus queue beneath the shelter. An old woman in front of her waved away the smoke.

A phone rang in her pocket. It was not her own. She took out an old-fashioned Nokia and answered it. She had not felt anyone place it there. ‘I said come alone,’ Mikhail said.

‘We’re not at the stage yet where I’m prepared to take that risk.’

‘Go to the S-Bahn station. Head for Westkreuz. Keep the phone with you.’

Kate put the Nokia back into her pocket and crossed the road. ‘He’s asked me to get on an S-Bahn train to Westkreuz,’ she whispered quietly into the microphone hidden inside the lapel of her jacket. ‘How the hell did someone get a phone into my pocket?’

‘Sorry, Kate,’ Danny replied. ‘We didn’t see anything.’

Kate bought a ticket and walked up the stairs to the platform on the floor above, which was shielded from the elements by a grand semicircular metal and glass roof. The station was crowded for this time of day, a large group of French schoolchildren moving slowly along it. Kate walked on beyond them to where a young man was circling on a battered scooter.

A train pulled in and she got on to it. The students boarded with her and she listened idly to the meaningless chatter of someone else’s children. The train pulled out. Grey buildings slid by beyond a rain-splattered window. The burner phone buzzed in her pocket. She answered it. ‘Get off at the next stop. Don’t end the call.’

The train rattled slowly into the station at Hackescher Markt. As the doors slid open, Kate did as she had been instructed. The voice at the other end of the line was silent. She waited. ‘Get back on. End the call.’

She did, just as the doors closed. The train pulled out. ‘I don’t know if I like this,’ she whispered into her lapel.

‘Let’s stay with it.’ It was Suzy, who must have been assigned to the makeshift control room. ‘We’re sticking with you, not far behind.’

‘Easy for you to say,’ Kate muttered. The train rolled on, past Museum Island and across the canal. The phone rang. ‘Get off at Friedrichstrasse. There is a coffee shop on the platform called Cuccis. Buy a coffee and wait.’

Kate was on the cusp of telling the voice at the other end of the line where he could stick his meeting, but he ended the call before she had the chance.

In the coffee shop, she ordered a black coffee and stood drinking it as the platform emptied, then slowly filled again.

The minute hand on the station clock crawled around the dial. Five minutes became ten, then turned into fifteen and finally twenty. ‘I’m crying off,’ Kate said.