He walked around the yard, trying to think it through. Didier’s work was well known around the village. It presupposed that anyone watching him for any length of time would soon come to know his routine. And if Claude was correct about the kind of ordnance lying around in the countryside, he had an almost inexhaustible supply from which to choose. That meant he would spend relatively little time out searching, but a lot more here in his yard.

‘The door’s open.’ Claude nodded at the house. The front door was sagging on its hinges.

It was too inviting to ignore. Rocco pushed the door back and stepped inside, ducking his head beneath the low frame.

The smell was the first thing to hit him. Sour with sweat, unwashed clothes and burnt cooking oil, the choking atmosphere was enough to make his stomach revolt. The light was poor, with heavy net curtains over the windows, now free of glass. The furniture was ancient, darkened by smoke and grease, with any visible surfaces covered in dust and mouse droppings, the remainder laden with dirty crockery, filled ashtrays and cooking utensils. Old newspapers and magazines spilt over from chairs onto the floor, most of them trodden flat and shredded beyond recognition.

There was no obvious sign of a telephone, he noted.

Three doors opened off the room. One led into a sleeping area of sorts, made up with a single, unmade metal-framed bed with no sheets and shabby blankets, a wardrobe and matching sideboard on a bare wooden floor. A single bulb hung from the ceiling, a nipple of brown grease hanging from the thin glass. A second door led to a narrow stairway, but it was soon evident by the layer of dust on the treads that it hadn’t been used in years.

The third door was locked, with a stone step just visible at the bottom. A cellar, Rocco guessed. He studied the lock. It was ancient but solid, and he decided to leave it. If there was anything down there worth seeing, he could come back another time.

‘You see this?’ Claude was standing by a small side table. Nailed to the wall above it was a bulletin board, the kind used by every police station, school and council office in the country. Among the various bills and notes pinned to it were several photographs, faded and discoloured by age and the toxic atmosphere of the room. Most looked like family groups, taken in the Thirties, judging by the style of clothing. But the one Claude was pointing at looked different. It wasn’t old, not in contrast to the others, which were faded and grimy, although the subject matter clearly was. It had been pinned on top of the others, where its size and freshness made it stand out.

‘Interesting,’ Rocco murmured.

The photo showed a group of six men and one woman, huddled around a campfire. Their faces were gaunt, the expressions sombre and inward-looking. One man was turned away, his face blurred, but the others were staring into the camera. They all held rifles, and one or two had bandoliers of ammunition slung across their chests. The woman was holding a pistol in one hand and a dagger in the other.

‘Resistance fighters,’ said Claude. ‘Maquisards. I’ve seen pictures like this before, but not often. It was taking a hell of a risk having your face recorded like that. The Germans would have paid good money for this kind of evidence.’

Claude ran a fingertip across the faces, stopping on a thin individual sitting next to the woman. The man looked about forty years of age, although he might have been younger, and appeared to be leaning against the woman, with one hand resting on her knee. He wore a heavy jacket and a beret and, like the others, looked as if he had not eaten or washed in days.

Claude tapped the man’s face. ‘Look who we’ve got here.’

Rocco looked. Felt a jolt of recognition.

It was Didier Marthe.

‘Did you know he was in the Resistance?’ said Rocco. He slid the photo into his pocket: it would be another line of enquiry to consider, although he didn’t hold out much hope of turning up anything useful. As Claude had said, the records of Resistance members were sketchy, and those in the know were inclined to be very secretive on the subject. In any case, it might not have any bearing on why someone had tried to kill the man.

‘I never heard him say anything.’ Claude shook his head in wonderment. ‘You occasionally hear of someone being involved – usually after their death. But it’s not something people talk about.’ He shrugged. ‘Those who do are usually the ones who like to suggest they were part of it, but weren’t, if you know what I mean.’

Rocco nodded. It was the same with the Indochina campaign: those who had been there talked about it the least. He’d come across the braggarts himself. Sad, most of them, to be pitied for their pretence and their false lives. ‘It might explain where Didier got his knowledge of explosives.’

‘True. But so what? It’s just an old photo.’

Claude was right; it was just an old photo. And unless he could come up with a plausible reason for Didier having plastic explosives and detonators in his home, he was making a puzzle where one did not exist.

As they walked outside, he automatically checked for signs of a telephone wire running into the house. He couldn’t see one … but neither could he imagine Didier Marthe having many friends to chat with, either on the phone or face-to-face.

Later that afternoon, he took a walk round the garden, trying to empty his mind of conflicting thoughts about the dead woman and the nearly dead Didier. Two events in such close proximity in Paris would have been unremarkable: murders and assaults with no obvious bearing on each other occurred in adjacent streets every day. It was the way of things in heavily populated areas. But out here in the middle of nowhere? It didn’t seem feasible.

He stopped beneath an old cherry tree and took out the photo of Didier Marthe and his fellow Resistance members. He turned it over. There was nothing to identify the group: no names, location or date scribbled helpfully for him to pursue. But there was a small blue stamp, an ink mark in one corner, in the shape of a triangle. He peered more closely and was able to decipher three letters, one on each side of the triangle. APP. The developer’s name?

He went back indoors and rang Amiens, asked to be put through to Massin. The commissaire came on and went immediately on the offensive.

‘Rocco, why are you involved with some idiot who wants to blow himself to bits? Your time is too valuable to waste on low-level misdemeanours.’ Clearly, the officer at the hospital had wasted no time spreading the word about Didier’s injury and Rocco’s presence at the hospital.

‘It might not be what it seems,’ explained Rocco, cutting him off short. He wanted Massin’s help, not to be tied up with pointless arguments about jurisdictions or the parameters of his work.

‘What do you mean?’

‘It’s true the wounded man was messing about with a grenade, but I think it had been booby-trapped with plastique.’ He took a deep breath and launched into his next statement before he could change his mind. ‘There might be a Maquis connection.’

There was a long silence on the line, and Rocco could picture Massin sitting back and judging how ill-advised it could be to go trawling into the murky history of the wartime Resistance movement. Others had been drawn into it before when revenge killings occurred or old scores were settled. It was usually messy and unpleasant, with many of the people now in positions of power. Suddenly having their past deeds exposed to the harsh light of a modern-day murder investigation was something most of them wanted to avoid, and digging too deeply into them could threaten the future prospects of an unwary investigator.

‘How do you arrive at that conclusion?’

Rocco explained about the photograph and its logo. ‘It looks as if Marthe might have been in one of the Resistance groups. The only link is the photo shop which processed the print, but I don’t have the resources or the leverage here to find it. I was hoping you could arrange a search.’