Were there any motives immediately apparent? Mark and Tina had had a row, and maybe he had lashed out and run off after starting the fire. Certainly possible, if his alibi was false. Banks turned to PC Smythe. “Constable, would you put the cuffs back on and take Mark here up to headquarters. Turn him over to the custody officer.”

Mark jerked his eyes toward Banks, scared. “You can’t do that.”

“As a matter of fact, we can. For twenty-four hours, at least. You’re still a suspect and you’ve got no fixed abode. Look at it this way,” he added. “You’ll be well treated, warm and well fed. And if everything you’ve told me is true, then you’ve nothing to be afraid of. Do you have a criminal record?”

“No.”

“Never got caught, eh?” Banks turned to Smythe. “See that his hands and clothing are checked for any signs of accelerant. Just mention it to the custody officer. He’ll know what to do.”

“But you can’t believe I did this!” Mark protested. “What about Tina? I love her. I would never hurt her.”

“It’s routine,” said Banks. “For purposes of elimination. This way we find out you’re innocent, so we don’t have to waste our time and yours asking pointless questions.” Or we find out you’re guilty, Banks thought, which is another kettle of fish entirely.

“Come on, lad.”

Mark hung his head and Smythe put the handcuffs on again, took his arm and led him to the patrol car. Banks sighed. It had already been a long night and he had a feeling it was going to be an even longer day as he saw Geoff Hamilton walking along the canal bank toward him.

Mist clung to the blackened ruins of the two barges as Banks, crime scene photographer Peter Darby, SOCO Terry Bradford, and FIO Geoff Hamilton climbed into their protective clothing, having been given the green light to inspect the scene by the station officer, who was officially in charge. Annie stood watching them, wrapped tightly in her greatcoat.

“This isn’t too difficult or dangerous a scene,” Hamilton said. “There’s no ceiling left to fall on us, and we’re not likely to sink or fall in. Watch how you go, though. The floor is wooden boards over a steel shell, and the wood may have burned through in places. It’s not a closed space, so there should be no problem with air quality, but you’ll still have to wear particle masks. There’s nasty stuff in that ash. We’ll be stirring some of it up, and you don’t want it in your lungs.” Banks thought about all the tobacco smoke he’d put in his lungs over the years and reached for the mask.

“Got a film in your camera?” Hamilton asked Peter Darby.

Darby managed a smile. “Thirty-five-mill color. Okay?”

“Fine. And remember, keep the video running and take photos from all angles. The bodies will probably be covered with debris, and I want photos taken before and after I remove it. Also, photograph all possible exits, and I want you to pay particular attention to any hot spots or possible sources when I tell you.”

“Basically every square foot, at least twice, while videotaping the entire search.”

“You’ve got it. Let’s go.”

Darby shouldered his equipment.

“And I don’t want any of you under my feet,” Hamilton grumbled. “There’s already too many of us going over this scene.”

Banks had heard the complaint before. The fire investigation officer wanted as few people as possible on the boats to lessen the chance of destroying evidence already in a fragile state, but he needed police and SOCO presence, someone to bag the evidence. Not to mention the photographer.

Banks adjusted his particle mask. Terry Bradford picked up his bulky accessory bag, and they entered the scene, starting with Tom’s barge. Banks felt a surge of absolute fear as he stepped onto the charred wood. One thing he had never told anyone was that he was terrified of fire. Ever since one particular scene back when he was on the Met, he’d had recurring nightmares about being trapped on a high floor of a burning building. This time it wasn’t so bad, he told himself, as there were no flames, only soggy debris, but even so, the mere thought of the flames licking up the walls and crackling as they burned everything in their way still frightened him.

“Go carefully,” Hamilton said. “It’s easy to destroy evidence at a fire scene because you can’t see that it is evidence. Fortunately, most of the water the fire hoses sprayed has drained over the side, so you won’t be ankle-deep in cold water.”

All Banks knew, as he forced himself to be detached and concentrate on the job at hand, was that a fire scene was unique and presented a number of problems he simply didn’t encounter at other crime scenes. Not only was fire itself incredibly destructive, but the act of putting out a fire was destructive, too. Before Banks and Hamilton could examine the barges, the firefighters had been there first and had probably trampled valuable evidence in their attempts to save lives. The damage might have been minimized this time because the firefighter who spotted possible signs of arson had some knowledge of fire-investigation techniques, and he knew they had to preserve the scene as best they could.

But of everything, Banks thought, it was probably the sheer level of destruction caused by fire that was the most disturbing and problematic. Fire totally destroys many things and renders others unrecognizable. Banks remembered from the warehouse fire how burned and twisted objects, which looked like nothing he had ever seen before – like those old contests where you’re supposed to identify an everyday object photographed from an unusual angle – had definite shape and identity to Hamilton, who could pick up a black shapeless object, like something from a Dalí painting, and identify it as an empty tin, a cigarette lighter or even a melted wineglass.

The barge was about thirty or thirty-five feet long. Most of the wooden roof and sides were burned away now, exposing the innards as a maze of blackened and distorted debris – sofas, shelving, bed, chest of drawers, ceiling – all charred by the flames and waterlogged from the firefighters’ hoses. One part of the room looked as if it had been dominated by a bookcase, and Banks could see soggy volumes lying on the floor. He couldn’t smell the place now, through his mask, but he’d smelled it from the canal side, and the acrid odor of burned plastic, rubber and cloth still stuck in his memory. As most of the windows had exploded, and the stairs and doors had burned away, it was impossible to tell if anyone had forced access.

Banks walked carefully behind Hamilton, who would stop every now and then to make a quick sketch or examine something, instructing Terry Bradford to pop it into one of his evidence bags. The three of them moved slowly through the ruins. Banks could hear the whir of the camcorder, which he held while Peter Darby took still photographs on Hamilton’s instructions.

“This looks to be where it started,” said Hamilton as soon as they got to the center of the living quarters.

Banks could see that the fire damage here was greater and the charring went deeper in certain areas than anywhere else they had seen yet, in places gathering in pools. They had to go slowly to make their way through all the debris littering the floor. Hamilton’s voice was muffled by his mask, but Banks could make out the words clearly enough. “This is the main seat. You can see that the burning on the floor is more severe than that on the underside of this piece of roofing.” He held up a piece of partially burned wood. “Fire moves upward, so the odds are that it started at the lowest point with the worst degree of burning. This is it.” Hamilton took off his mask and instructed Banks to do the same. Banks did so.

“Smell anything?” Hamilton asked.

Amid the mingled odors of ash and rubber, Banks thought he could smell something familiar. “Turps,” he said.