She almost ran through the bright concourse to the pedestrian section of Komsomolskaya Square beyond. She stopped by the line of yellow taxis and looked back over her shoulder at the clock tower above the station. It was eight thirty. She glanced about her. If they were watching, she certainly wasn’t in a fit state to pick them out from the huge thronging crowd of early-morning commuters. She briefly considered getting into a taxi or heading straight back to catch a return train to St Petersburg.

She brought up Google Maps. She needed somewhere to sit, to think. She found Sokolniki Park was only a short distance away and walked there fast, oblivious to the people around her.

There was an Orthodox church adjacent to the park, so she installed herself in a pew at the back and closed her eyes. The moment she did so, she conjured an image of Sergei’s face, his eyes bulging with the pain and shock of his sudden death. She hadn’t seen any particular sign of a struggle: had it been someone he knew, expected even?

Who could have killed him? And why?

She wasn’t on the passenger manifest but they must have watched them get on the train. If so, why had she been spared? Kate tried to pull herself together. She looked around the empty church.

She walked to the entrance and peered out. Two women in long trench coats leant against an iron fence by the road, as if waiting for her. She retreated again.

On an instinct that she later spent a great deal of time trying to analyse, Kate decided to call Stuart. He answered on the third ring, as if he had somehow been expecting her call. That was almost enough to prompt her to ring off straight away, but not quite: she was desperate. ‘Hi, love,’ he said, ‘how nice to hear you.’

‘Where are you?’

‘Er, at home. Well, if you can call it that. In my apartment in Moscow.’

‘I need your help.’

There was a momentary pause. ‘Of course. How?’

‘I’m in Sokolniki Park. There’s an Orthodox church. I’m sitting at the back of it. Please come and get me.’

‘In Moscow?’

‘Yes.’

‘Jesus, Kate, what are you doing here?’ If he had truly expected this call, then his surprise was well faked.

‘I just need your help urgently. I don’t know if it will cause trouble for you and, well, I’ll understand if you want to turn me down.’

‘Of course I’ll help you. I’ll leave now. Just keep your phone on.’

Kate went back to the entrance and peered through the doorway. The two women had moved off. She stepped out and looked up and down the street, but there was no sign of either of them.