Chavasse closed the door and moved quickly along the corridor. He mounted the steps at the far end, opened another door and found himself in a narrow passage that opened into the main hall.

There was a tiny glass office by the entrance and two guards were sitting in it drinking tea. He walked steadily forward, keeping his head down, and one of the guards looked over his shoulder, called something and laughed, exposing decaying yellow teeth. Chavasse waved a hand casually and went out into the night.

A jeep was parked at the bottom of the steps, its canvas hood raised against the rain. He hesitated for only a moment before going down the steps quickly and climbing behind the wheel. The engine roared into life at the first touch of the accelerator and he released the handbrake and drove slowly away.

He waited for the sound to come from behind, for the sudden cries of alarm, but nothing happened. There was a soldier on duty under the light at the main entrance, a submachine gun crooked in his arm. Chavasse slowed to stop, but the man raised an arm and waved him on. He turned into the square outside and drove down into the centre of Changu.

When he parked the jeep in the courtyard outside Hoffner’s house, the rain was still drifting slowly down and it was cold and raw. It had been easy – almost too easy – and as he mounted the steps to the front door he felt no particular jubilation. He was tired, very tired, and curiously light-headed.

When he pulled on the chain, the bell echoed into the darkness inside. He leaned against the door and when it opened suddenly he staggered forward.

And then he was safe – truly safe. Arms reached out to steady him, soft arms, but with strength in them for all that, and Katya Stranoff’s face glowed out of the half-darkness.

It was pleasant and far removed from the world outside, from the rain drumming against the shutters; Chavasse relaxed, the warm fire on his bare chest, and watched Katya make tea by the hearth.

Hoffner sounded him with a stethoscope, his face intent. After a while he straightened and shook his head. “You should be in hospital, Paul. Physically, you’re in a terrible state.”

“My condition’s hardly likely to improve if I stay round here for much longer,” Chavasse said. “What I need is something to keep me going for a while. Can you do anything?”

Hoffner nodded. “But only for a limited time.” He turned to his black bag and took out a small glass ampoule and a syringe.

“How long will that last?” Chavasse asked.

“Under ordinary circumstances, twenty-four hours,” Hoffner said, “but in the state you’re in, I can’t be sure. I can give you this and one more. Two days at the most. After that you’ll be flat on your back.”

“But safe across the border into Kashmir.”

He hardly felt the needle go in, and as soon as it was withdrawn he started to dress again hurriedly. Katya turned and handed him scalding tea in a porcelain bowl and he raised it to his mouth and drank greedily.

“When do you intend to leave?” she said.

He frowned. “When do I intend to leave? Butwe’re all going.”

She placed a hand on his knee and said earnestly, “You must try to get out, Paul, that I can understand, but Doctor Hoffner is an old man. It’s at least a hundred and forty miles from here to the border, over rough country. He’ll never make it.”

“I’ve got a military jeep standing in the courtyard with a tankful of petrol,” Chavasse said. “We can drive from here to the other side of Rudok, leaving the jeep at the foot of the Pangong Tso Pass and go through on foot for the last two or three miles.”

“But his heart won’t be able to stand the altitude,” she insisted.

Hoffner brought her to her feet and placed his hands on her shoulders. “Katya, I’ve got to go. You must understand that, but I want you to come with us more than anything else in the world.”

Chavasse buttoned his quilted tunic and stood up. “I’d like to remind you that we haven’t got much time. They’ll discover I’m missing within the next half hour at the outside.”

She shook her head. “But why is it so imperative? There’s something here I don’t understand.”

Hoffner glanced at Chavasse, eyebrows raised, and Chavasse nodded. The old man looked down at her and said gently, “I’m afraid we haven’t been completely honest with you, my dear. You see, I’ve made a discovery of some importance. A significant new contribution to mathematical concept.”

“And that’s the understatement of the age,” Chavasse said.

Hoffner ignored him and continued, “This discovery means that I have suddenly become important, not only to my own country, but to the entire Western world.”

Her face was completely expressionless, and yet there was pain in her eyes. “Why didn’t you tell me this before? Didn’t you trust me? Do I mean so little to you?” She turned to Chavasse. “To either of you?”

“But it would be asking so much,” Hoffner said. “To turn against your own people. To live amongst strangers for the rest of your life.”

She lifted one of his hands and held it against her cheek. “You are my people.” She turned and smiled straight at Chavasse. “You and Paul. Who else have I got in all the world?”

Chavasse pulled her into his arms and when he kissed her, her face was wet with tears. She smiled happily as she looked up at him, and then her smile died.

He felt a cold breath of wind from the outer hall as it touched the nape of his neck, and something seemed to crawl up his spine. He pushed Katya away and turned slowly. Captain Tsen stood just inside the doorway, Hoffner’s Chinese houseboy beside him, a machine pistol in his hand.

There was an expression of unholy joy on Tsen’s face and his teeth gleamed in the firelight. “So, at last we have the truth, Mr. Chavasse? I’m sure you’ll agree it was well worth our little stratagem, but now the playacting is over.”

He should have known, Chavasse told himself bitterly. The whole damn thing had been too easy. To Colonel Li, who knew his man, the escape was something he had counted on. Just another move in the game, and one that had paid off.

Hoffner took a step forward, pushing Chavasse to one side. “Now look here, Captain,” he began.

“Please stay exactly where you are,” Tsen told him coldly.

For a brief moment the houseboy’s eyes flickered towards Hoffner, and it was all Chavasse needed. He gave Katya a push that sent her staggering out of harm’s way and dived for the safety of the shadows behind a wing-backed chair.

As the houseboy swung the machine pistol in an arc, bullets spraying the furniture, Katya ran forward shouting, “No, Paul, no!” and then she screamed and fell to the floor.

She lay on the sheepskin rug in front of the fire, blood pouring over her face from a wound in her forehead. Chavasse crouched for a moment to the side of the chair and peered round the edge.

The houseboy and Tsen were still standing in the doorway and Hoffner was kneeling over Katya. “You can’t get away, Chavasse,” Tsen cried. “Come out with your hands up.”

Chavasse crawled on his belly behind an antique divan and carefully lifted a small Chinese ornament from a table beside him. He hefted it in his hand for a moment.

“I’m running out of patience,” Tsen cried.

Chavasse lobbed the ornament across the room into the shadows of the far corner. The houseboy turned and fired twice in rapid succession and Chavasse stood up, took three quick paces forward and hit him across the back of the neck with the edge of his hand. He grabbed the machine pistol as it fell from nerveless fingers.

Tsen had only just managed to get his automatic out. He dropped it hurriedly and Chavasse bent to pick it up and slipped it into his pocket.

“There’s only one thing keeping you alive,” he said. “The fact that I happen to have a use for you. Now take off your belt and turn round.”