‘Just turn your car round and head back to Madrid, OK? We’ll catch up on Wednesday. Just sit tight until then.’

He gives me an address in Tetuán, which I assume to be the SIS safe house, and a time – two o’clock on the afternoon of the 16th. Then we say goodbye and, against his express wishes, I pull the car back onto the motorway and continue into Castilla-La Mancha. The village lies about eight miles north of Sigüenza, a cathedral city which was once a front line for nationalist troops in the Civil War. This is Cervantes country, the bare plains and rolling hills and ruined forts of Quixote and Sancho Panza. Two thousand years ago there was a Roman presence here and the road runs in a pure straight line all the way to Valdelcubo, which turns out to be an archetype of the rural Spanish pueblo: crumbling, deserted, dusty. Boys are kicking a football against the wall of a pelota court in the centre of the village, but so many strangers have passed through today that they no longer bother to look up when I drive past. At a café just off the main square, television crews from TVE, Telemadrid and Euskal Telebista are eating bocadillos and slices of tortilla in the window and I worry that the Audi might draw their attention. Kitson’s words are echoing in my ears and he might have a source here who will report back if my car is sighted.

Driving out of the square I head down a narrow street barely wide enough for a single car and simply follow the scent of the story. A steady, ant-like stream of cops and hacks are funnelling back and forth from the countryside, although by the time I reach the scene only a sprinkling of bystanders remains. Parking the Audi next to a pile of timber and encrusted manure, I walk to a high point from which it is possible to observe the entire area through 360 degrees. The landscape is breathtakingly beautiful and, before my gaze falls on the horror of Mikel’s impermanent grave, I find myself regretting the fact that I have spent so little time in this region over the past six years. Whatever happens, these will be my final weeks in Spain. When it’s over, when Arenaza’s killer has been jailed and Kitson moved on to pastures new, I will be obliged to leave, either to take up his offer of a renewed career with SIS, or to live in some as yet undisclosed location, there to rebuild the lies and the paranoia of Madrid, to discover new haunts and safe houses, to find another Sofía.

Arenaza’s body has been completely removed. That much is immediately clear. A lone forensic scientist is examining the scene, planting her legs awkwardly as she encircles the grave, like someone walking through deep snow. When did they bring him here? Was Rosalía waiting near by? It’s hard to imagine that the woman I followed and observed day after day could have involved herself in something as diabolical as murder. Why jeopardize her career, her relationship, for vengeance? Why involve herself with a man like Luis Buscon? Perhaps Gael played a part in the entrapment. Perhaps that’s where Kitson should be looking. An old man, clearly local, with age lines cut through his cheeks like scars from the sun, comes and stands beside me, muttering something about Batasuna being ‘the enemy’. I move away from him with a nod and get back in the car.

One of the tracks leading back to the main road passes beside an old wall that is in the midst of being rebuilt. Fresh blocks of grey stone have been placed next to a hut in a small clearing, and there’s a freshly constructed wooden cross planted at the top of a low summit looking out over the western side of the village. I put out my indicator and wait for a car to pass before making the turn back into Valdelcubo. Just as I am preparing to pull out, Patxo Zulaika walks past the passenger window, holding a small baby in a harness attached to his chest. His eyes ignite. Peering through the window, he stares at my face, fingers raised to tap on the glass.

I manage to say, ‘Patxo, I thought I might see you here,’ before my throat blocks and dries up in panic.

‘I cannot say the same about you,’ he replies. I slide the window down, erasing my reflection, trying as best I can to look relaxed.

‘Well, I saw what happened on TV. Had the morning off so I drove up to see for myself.’

He looks at me for a long time, drawing out the stare, as if to check the validity of my entire existence. Then his eyes scan the back seat and he purses his lips.

‘So, you reporting for Ahotsa?’ I ask, just to break the silence. Zulaika is the kind of man who obliges you to break silences.

‘That is right. And you? You are leaving, Alec?’

I see that the top of his baby’s head is chapped with cradle cap.

‘Yes, I have to go back to work.’

‘Oh. Well I am also going to Madrid for the night. Perhaps you have time for a coffee?’

There’s no getting out of it. If I make an excuse and drive off he will only force my hand at a later point. This is exactly what Kitson feared. This is what he was talking about on the motorway.

‘Sure. But I can’t be long. I have to drive down to Marbella later on for a few days. Where do you want to go?’

He suggests that I follow him onto the motorway. There’s a busy roadside garage about fifteen kilometres south of Sigüenza where we can talk in private, away from the pricked ears of journalists and Guardia Civil. Now that he needs me, now that he wants some answers, Zulaika has added a courteousness, even a finesse, to his manner. He introduces his baby son – little Xavi – with a proud father’s enthusiasm and excuses himself for five minutes while he retrieves his car. I’m going to have to play this one very carefully. He’s onto me. Zulaika is very smart and very thorough and he will stop at nothing to get to the bottom of whatever it is that he believes I’m concealing.

He drives fast and we arrive at the petrol station just after 3.30. Inside he selects a table at the rear of the restaurant and obliges me to sit with my back to the room. Zulaika then announces that he’s hungry and orders salad and fabada from the menú del día. That was sly: now we’ll have to sit here talking until he has finished his food. With nothing to lose, I too order lunch and the first course arrives within three minutes. He has put Xavi in a rocker on the floor and the waitress keeps bending over to coo at him.

‘I didn’t know you had children.’

‘Well, we don’t know each other,’ he says. ‘Why should you?’

Now that he has me where he wants me, normal service has resumed. The manner is once again curt and to the point.

‘Did you drive down from Bilbao this morning?’

‘That is right. My wife had to go to England last night so she left me looking after the baby.’

‘She went to England?’

‘Yes. She has family there. Her grandmother is very sick.’

It is illustrative of my incessant paranoia that I briefly forge links in my mind between Zulaika and SIS. The conspiracy goes something like this: Kitson knew that I would not be able to resist coming to Valdelcubo, so he tipped off Zulaika – who is a source for MI6 – and hopes, in the long term, that the Spanish press will frame me for Arenaza’s murder. The theory is completely absurd, and yet it is three or four minutes before I regain my composure, a period in which Zulaika has been talking in Basque on his mobile phone. He may have been checking his copy with the sub-editors at Ahotsa, but it’s impossible to tell.

‘Do you understand Euskera?’ he asks.

‘Not a word.’ My salad has a lot of raw white onion in it and is otherwise composed of greying shreds of iceberg lettuce and some overripe olives. I set it to one side and watch as Zulaika eats his. ‘So what was it that you wanted to talk about?’

I time the question so that he has his mouth full of food; it’s a good twenty seconds before he is able to respond.

‘Well, I have to say that I was surprised to see you there today, Alec.’