‘It’ll be Miss Marple all over again,’ he had told her. ‘Put on a show like the one in Nice and we’ll put you up for a BAFTA.’

Spying is waiting.

On the Thursday evening, with Amelia still in London and Vincent still in Paris, Harold and Barbara had driven into Salisbury to watch a film, leaving Kell and Elsa alone in the house with nothing to do but reminisce about Nice and to work through the final details of the operation.

‘Amelia is going to try to persuade Vincent to go for a walk with her on Saturday morning. If the weather’s bad, she’ll suggest visiting a pub near Tisbury for lunch. Either way, we should have enough time to get into his room and soak his gear. There’s no mobile reception in the valley, so if we’re lucky, he might have switched off his phone and left it behind as well.’

‘This would be very lucky, I think,’ Elsa replied. She had three separate gold studs in her left ear and Kell kept staring at them, thinking of her other lives. ‘All I need is fifteen minutes with the laptop. I can copy over everything from his hard drive, then bring it back here for analysis. If he’s getting emails from his people, we can start to read them. If they are being careless, we might be able to trace where the messages are coming from.’

‘What do you mean “if they’re being careless”?’

‘Anybody serious wouldn’t email from the location where they are holding Amelia’s son. They would drive a few kilometres away, do it from there. People often keep a device for that purpose away from the base. But it can be a pain working like this and sometimes people get lazy.’

Kell thought of Marseille, of his own computer stripped down by Luc and handed back, complete with key-logger software and the tracking device. He had told Elsa about the attack in Cité Radieuse and she had touched the scar on his face, a tenderness which had surprised him. In Nice, he had been concerned that Elsa was playing him, most likely at Marquand’s request, but there was surely now no reason to doubt her.

‘You were a little dismissive with me the first time we met,’ she said.

‘I was working,’ he replied.

‘This is fine. I expected it. Jimmy told me that you could be … what is the word?’

‘Wonderful?’

A swipe of laughter. ‘No. Impatient. A little arrogant …’

‘Brusque.’

Elsa had never heard the word before. She tried it out, rolling it around, and decided that it was adequate enough as a description of Thomas Kell. ‘Brusque, yes. Then later on, much kinder to me. I liked our conversations.’

He was surprised by her flirting, but enjoyed it. She had a way of dismantling his professional veneer, of strolling into the more private rooms of his personality with what felt like the fearlessness of youth.

‘You did a fantastic job,’ he said, and meant it. The research Elsa had done into Malot’s background had unlocked the DGSE operation and led him to Christophe Delestre.

‘Let’s eat,’ she replied.

The day before, Harold had stocked up on ready-meals for the team at a supermarket in Salisbury. Opening the fridge at lunchtime, looking for something to eat, Elsa had dismissed the food as ‘disgraceful’ and duly set about making a batch of fresh pasta in the kitchen. Within half an hour, she had transformed the room into a bombsite of bowls and dough, flour hanging in the air like the dawn mists over the Chalke Valley. Now she cooked the pasta for Kell, who opened a bottle of wine from Shand’s cellar and sat at the kitchen table, watching as she chopped courgettes, frying them in garlic and olive oil.

‘You look like you know what you’re doing.’

‘I am Italian,’ she replied, happy to bask in the stereotype. ‘But in return for your supper, I want to hear all of Thomas Kell’s secrets.’

‘All of them?’

‘All of them.’

‘That may take a long time.’

He did not want to talk about his marriage; that was his only boundary. Not out of loyalty to Claire, but because the story of their relationship was a story of failure.

‘Start with why you left the Service.’

He had been drinking wine and stopped the glass against his lips, surprised that Elsa had broached the subject of his disgrace.

‘How did you know about that?’

He was not angry; indeed, he felt an odd sense of relief, finding that he wanted to speak candidly of what had happened.

‘People talk,’ she replied.

‘It’s a complicated situation. I’m not supposed to discuss it.’

Elsa had put a pan on to boil. She looked at him with a quick, mock contempt and threw salt into the water.

‘Nobody is going to hear us, Tom. We are alone in the house. Tell me.’

And so he told her. He told her about Kabul and he told her about Yassin.

‘After 9/11, I did a lot of work alongside the Americans. They were angry about what had been done to them. Understandably so. They were ashamed and they wanted revenge. I think that’s a fair assessment of their state of mind.’

‘Go on.’

‘Late 2001, I went into Afghanistan with a team from the Office. Joint operation with Langley. All of us had been caught off guard by what had happened in Washington and New York. We were playing catch-up, making things up as we went along.’

‘Sure.’ Elsa was watching the pan, her back to him, waiting for him to find his rhythm. She was wearing blue denim jeans and a white T-shirt. Kell stole a married man’s glance at her body, all the time falling into the trap of trusting her.

‘I made seven separate visits to Pakistan and Afghanistan over the next three years. In ’04, the CIA arrested a man who you may have heard of. Yassin Gharani. He’d been in Pakistan where he’d attended an al-Qaeda training camp in the north-west. He told the Yanks he was a British citizen, had the passport to prove it. He’d subsequently been moved to their operations centre in Kabul, which is where they started to interrogate him.’

‘Interrogate.’

‘Interview. Question. Cross-examine.’ Kell wasn’t sure whether he was giving Elsa an English lesson or whether she was one step ahead of him on the semantics. ‘He had not been mistreated, if that’s what you’re driving at. Langley was informed by MI5 that they had a file on Yassin. He’d been on a watch-list of terrorist suspects in the north-east of England. Not a flagged threat, not a target, no surveillance. But they knew about him, had been worried about him, they’d wondered where he’d gone.’

‘So it makes sense to everybody that a young man like this goes to Pakistan and trains to fight?’

‘It makes sense.’ Kell poured himself more wine and stood to refill Elsa’s glass. She had fried the courgettes and set them to one side in the pan and now slowly lowered the pasta into the water.

‘Thank you,’ she said, nodding at the glass. ‘The tagliatelle, it takes only a couple of minutes.’

Kell took two bowls from a dresser beside the kitchen door, retrieved spoons and forks from a drawer. He put the cutlery on the table in front of him, the bowls next to the stove so that Elsa could reach them. Then he picked up the story.

‘Now here’s Gharani, a twenty-one-year-old student from Leeds, pretending to be visiting friends in Lahore, but the Americans have photographic evidence that Yassin is a jihad tourist who just got taught how to fire a rocket-propelled grenade in Malakand. I told him he had to be careful. I told him that his best prospect lay in talking to his own government. If he was honest about what he had done, about the people he knew back home, then I could help him. If he wasn’t, if he decided to keep quiet and keep playing the innocent, then I couldn’t be responsible for what the Americans would do with him.’

‘I know this story,’ Elsa said. She tested the pasta, pulling a single strand from the water and pressing it between her fingers. She wrapped a tea towel around the handle of the pan, took it to the sink and poured the contents into a metal colander, steam fogging into her face. She reared back and said: ‘The CIA tortured him, yes?’