The house was all in darkness and Harry moved quietly through it. She knew it so well that she could anticipate each creak of the stairs, every uneven part of the floorboards. It was like a virtual map in her head, an instinctive knowledge that she felt would stay with her forever.

She reached the bottom of the sweeping staircase and stood still, listening intently. The ground floor was all in silence; she could discern no sign of any disturbance at all. She did a quick sweep of the main entrance hall and then moved towards the kitchen and a back door entrance that she knew was little used. Passing the scullery, she heard a sound. She stopped. The noise came again – a faint whine, followed by a scrabbling. Suddenly, her face relaxed and she turned the heavy knob that held the door shut. A second later, Jasper was jumping up to greet her, delighted to have a visitor at this unlikely hour. He licked her hands and gave a little bark, then quietened down as she laid a warning hand on his head.

Harry calmed him, whispering to him softly; strangely comforted by the feel of his hot breath on her face. He gazed deeply into her eyes as she crouched down beside him and seemed to be attuned to the adrenalin that was coursing through her body. She paused for a moment, deliberating, and then quickly she flicked on the light in the scullery, searching the shelves until she found what she was looking for.

"Be a good dog now and help me," she whispered to him, clipping the nylon lead onto his collar, and then turning the light off again. Jasper wagged his tail, and they left the scullery and moved towards the side door exit at the end of the hall.

Harry unbolted the heavy door and pulled it open; together, they slipped out into the freezing dawn. She wore dark jeans, a thick sweater and a jacket, but in her haste, she hadn't had time to seek out gloves so the cold bit into her hands like a dozen gnawing teeth.

Her gun sat snuggly against her rib cage. She hesitated a moment before she fastened her coat buttons against the cold, but, she reasoned to herself, they could be undone in seconds if need be. She'd grabbed a small torch from the bedside cabinet, and now she turned it on, directing its narrow beam on to the snow.

In the bedroom she had paused briefly, considering whether or not to wake Dempsey. Her feeling was only a hunch and it could be nothing, even if the way her heart was hammering suggested otherwise. Finally, she decided to leave him to sleep.

She set off with Jasper down the steps that lead to the lawn. She kept him close, gripping the lead tightly in her left hand. He strained in front of her, trailing the snow with his nose until they found the footsteps she had seen from the bedroom window.

"That's it, pick up the scent," she whispered, letting him linger over the first of the deep prints. The moon had emerged from behind the thick clouds that had filled the sky earlier, and now it cast an eerie glow across the smooth lawn ahead of them. The indentations were clearly visible, and as they followed them, she saw that, as she had suspected, they lead to the neglected, secret place.

As they reached the copse, she stopped, listening. Nothing, only the faint rustle of branches in the winter wind. Just round the other side of the cluster of trees was the entrance to the long-forgotten air-raid shelter. It had been constructed during the Second World War and was big enough to house the Winfield family and their staff. The entrance itself was small, and designed to be unobtrusive. In fact, it would be easy to walk within a few yards of it and be oblivious to its existence, if one were not privy to it. It was reached by a set of stone steps that were now very over-grown. As far as Harry knew, no one had bothered to maintain the place for thirty years or more. She was very familiar with it, however. She had loved to play there as a child, it had seemed so exciting; a hidden underground cavern with labyrinthine passages. Her father had forbidden her from going there many times, not that she had heeded him; he deemed it unsafe and worried that the accumulation of years of bad weather would one day cause the roof to collapse in on itself. In addition, there were so many interlinking rooms; it would be easy to get hopelessly lost. Strangely, Harry had always instinctively felt safe in the shelter – she knew it was well constructed and despite the succession of terrible winters and heavy snowfalls, it had always remained completely watertight, with never a hint of damp.

It took her until she was almost at the top of the steps before she saw the light. She pulled Jasper's lead tighter until she felt his reassuring warmth against her leg. There was someone down there. The door was partially open, and she could hear movement inside and see the swinging glow of a faint light, as though someone were playing a torch over the walls and ceiling.

She crouched down beside Jasper, dropped his lead and placed her hand on the back of his neck. "Stay," she whispered, and felt him tense, standing dead-still. Slowly, she rose to her feet, but the dog didn't move a muscle. With a final glance back at him, she began to move down the steps towards the source of the light. Her buttons were undone, and her hand went under her jacket, feeling for the pistol there.

It was firmly in her grasp as she pushed the door open and peered into the musty space within. A dim paraffin lamp flickered in the corner, and in the centre of the room, a bulky figure was standing with their back to her, facing the wall. They were bending over something, intent on a task that Harry couldn't see.

Her heart was beating heavily. She wasn't sure what her eyes were telling her, only that this wasn't right. There was no reason for anyone to be down here; no other reason than that something was wrong. She made herself count slowly to five and then she tensed, pointing her gun firmly at the broad back in front of her.

"Freeze!" she heard herself say. "Police!"

She was sure that the person hadn't known she was there until then, but as they turned around, there was no surprise in their eyes.

"Hello Harriet," said Esther. The two women gazed at each other for a few moments before she spoke again.

"What on earth are you doing up at this time of night?" her tone of voice was mild, inoffensive. Her hair was pulled back from her head, hidden under a heavy shawl. In the dim lamplight, her face was paler than ever and her eyes glittered as she regarded Harry.

"Most unfortunate really. For you, that is."

"On the contrary...," Harry began, but she didn't finish. Someone had run softly down the stairs behind her, someone holding a heavy, old fashioned hunting rifle. The butt hit her hard on the side of the head and she sank to the floor before she had even registered that anyone else was there.