The silence was suddenly broken as a high-speed train roared into view beyond the wood-fringed fields to his left. The brightly lit carriages sped past in a barrage of sound – and were gone. Umber stood listening to the fading note of the engine. Then he pressed on.

A few minutes later, rounding the next bend, he saw a humpback bridge ahead and the pale line of a track leading up from it across the sloping field on the other side of the canal. And then he saw the dark shape of a boat moored just beyond the bridge. He stepped up the pace.

The bridge served only the track. There was no road in sight. An old wartime pillbox was half-buried in the undergrowth beside the towpath just beyond the bridge. The mooring was quiet and inaccessible. Umber could see no signs of life as he approached the boat. There were no lights showing at any of the windows. It was a smartly painted, well-maintained craft, roped fore and aft to stakes driven into the bank. Its name was lettered boldly on the prow: Monica.

Umber stepped into the bow area and voiced a hopeful 'Hello?' But the doors to the cabin were padlocked shut. Wisby was obviously not there. Umber peered in through one of the glazed panels in the doors, but could see nothing.

Then, as he stepped back, the padlock suddenly fell to the deck with a thump. Umber stared at it in bemusement. The loop had been snapped clean through. The pierced edges glinted up at him. Someone had cut through the lock, then replaced it loosely on the hasp. Umber's movements had been sufficient to dislodge it. It had been rigged to appear secure, whereas in reality…

He flicked the hasp back and pulled the doors open. The cabin was in darkness, the twilight seeping through the half-curtained windows scarcely penetrating the deep, jumbled shadows. He felt for a light switch, but could not find one. His fumblings did chance on a torch, however, hanging just inside the doorway. He unhooked it and switched it on.

The torch beam revealed what seemed at first to be an immaculate interior of polished wood and burnished brass, with nothing out of place. Then, about halfway down the cabin, the light fell on a slew of papers across the floor. They lay at the foot of a three-drawer metal filing cabinet – an incongruous sight aboard a narrowboat. There were discarded folders amidst the scatter of papers. Someone had ransacked the cabinet.

Umber was about to step into the cabin when he felt the boat lurch beneath him. As he turned, he saw a gap opening between the boat and the bank. A man in a black tracksuit was standing on the tow-path, staring straight at him – a man he knew from their encounter in Yeovil as John Walsh. Beside him, the stake was still planted firmly in the ground. But there was no rope tied around it.

For a second, Umber froze, his thoughts and reactions scrambled. Where had Walsh come from? The pillbox, perhaps? He could have hidden inside it as Umber approached. He must have broken into the boat, failed to find what he had been looking for, then lain in wait for Wisby. But it was not Wisby who had walked into his trap.

Walsh had untied the rope and shoved the boat away from the bank; But the rope at the other end of the vessel was still fastened, causing it to drift out diagonally across the canal. There was already too wide a gap to jump from the bow. Umber would have to reach the stern to get off. But he did not for a second believe Walsh meant to let him do that.

'You shouldn't be here,' Walsh shouted, shaking his head. 'You really shouldn't.' His gaze shifted suddenly away from Umber. In the same instant, there were heavy footfalls on the roof of the cabin.

Umber turned just in time to see a burly, camouflage-clad figure looming above him. He glimpsed the blurred arc of a baseball bat swinging towards him. He raised his arm to protect himself, the torch still clasped in his hand. The bat was aimed at his head, but the rubber barrel of the torch took the direct force of the blow.

Of this, Umber was in no real sense aware. Something had struck him a stunning blow. That was all he knew. Then something else struck the back of his head as he fell. And the rest was darkness.

Umber was cold. God, was he cold, shivering as he woke to a damp patter of rain on his face. Dreaming and consciousness collided in a jolt of blurred memory. He moved, wincing as a pain throbbed through his head. Slowly, he pulled himself up into a sitting position.

The night was inkily black. He could see virtually nothing. He put his hand behind his head and felt a tender, oozing lump. Then he noticed a feeble glimmer of light nearby and stretched towards it. It was the torch, its batteries all but exhausted. He switched it off.

He was still aboard the Monica. That was about all he could be sure of. The boat was rocking gently beneath him, the cabin doors creaking on their hinges. There was another sound, of wood thumping dully against wood.

He clambered awkwardly to his feet, his every movement slowed by dizzying pulses of pain in his head. The boat must be adrift, he reasoned. For all he knew, it was in the middle of the canal. But no. There was that thumping again. And he could make out the shadow of something beyond and above the cabin. A bridge, perhaps? No. It was too low. A lock gate, then? Yes. That had to be it. The Monica had drifted down to the next lock.

He felt his way round the bulwark to the side he had boarded by and reached out blindly into the darkness. Nothing. Then he scrabbled around the deck until he found the broken padlock. He tossed this in the direction of where he thought the bank should be and heard it fall to earth rather than into water. He pulled the left-hand cabin door wide open and, grasping its handle, stretched out further into the void, flapping his arm as best he could in search of a hold. Still nothing. He slumped back against the door, head pounding.

It was hopeless. He was going to have to phone for assistance: the police or an ambulance. He reached into his pocket for his mobile. Not there. It must have slipped out onto the deck. He lowered himself to his knees and felt around for it. The bow area was small. It did not take long to cover. But the phone was nowhere to be found. Then he understood. It was not there because Walsh had taken it, either to deny Umber the use of it or to listen to any messages left for him.

He crouched where he was, gathering his resources. To get off the boat, he was going to have to reach the stern. He could go through the cabin, but the aft door was bound to be locked. Walsh would hardly have broken in at both ends. No, the only ways off were along the outside of the cabin or over the top. There was a ledge either side of the cabin, Umber vaguely recalled, but it was desperately narrow. The roof was a marginally better option. He scrambled to his feet, waited for the ache in his head to subside, grasped what felt like a rail fixed to the roof, put one foot on the bulwark and pulled himself up.

In the same instant, the boat bounced against something, pitching Umber forward. His hand slipped from the rail. He lost his balance and fell.

It was the ground he hit, not water. The Monica had drifted into the bank. A jarred shoulder and a red mist of pain behind his eyes were worth it to feel mud and grass beneath him. He levered himself slowly upright and blundered forward like a blind man until he reached the jutting balance beam of the lock gate. He leaned against the beam for a minute or more, recovering his breath and what was left of his wits. He looked at his wristwatch. The luminous dial told him the time was a few minutes before nine. He would have guessed it was the middle of the night. But then so, in a sense, it was – for him.

The shaly surface of the towpath crunched beneath his feet as he took a few tentative steps away from the beam. Logically, if he kept to the path, with the canal to his right, he would make it to Newbury in the end. Kintbury was probably closer, but the frightening possibility that Walsh and the man who had attacked him were still waiting for Wisby by the bridge meant Newbury it had to be. He started walking.