As she followed the girl she became more and more agitated. Sherlock Holmes says you can’t disguise a back. Or maybe it’s Peter Wimsey. Anyway, from the back that girl sure looks just like the Mouse. She doesn’t walk like her, though. Valentina would never have moved with such forthright strides through a crowd. The girl ducked into Stanfords, the map shop, and Julia did too.

“Please, I’m looking for a map of East Sussex?” The girl’s voice was a rich alto, unmistakably Oxbridge.

“D’you want the road map or Ordnance Survey?” asked the shop assistant.

“Ordnance Survey, I think.”

Julia loitered at a table full of books about Australia while the girl followed the assistant downstairs. A few minutes later, the girl came up the stairs holding a shopping bag and Julia got a good look at her face.

She was like Valentina, and she wasn’t. There was an extraordinary resemblance, and none at all: the girl had Valentina’s features, and none of her expression. The girl was heavily made up, with dark lipstick and eyeliner. Her eyes were brown, and her face had an assurance that Valentina could never have matched. She radiated confidence.

The girl had her hand on the door; she was about to slip away, and Julia couldn’t bear to let her go.

“Excuse me,” said Julia. The girl stopped and turned, saw that it was herself that Julia meant to address. Julia saw that the girl was pregnant. Their eyes met: was the girl surprised? Afraid? Or just startled to find a stranger’s hand clutching her arm?

“Sorry?” the girl said. Julia stared so hard she felt as though she were eating the girl’s face. She wanted to scrub off the make-up, to undress the girl to see if all the familiar moles and vaccination scars would be there.

“You’re hurting me,” said the girl loudly. It wasn’t Valentina’s voice. Around them the shop went still. Julia heard heavy footsteps behind her. She let go of the girl’s arm. The girl flung open the door, stepped onto the street and hurried away. Julia followed her out and then stood watching as she disappeared into the crowd.

Elspeth forced herself not to run. She was panting, and she tried to slow down. She didn’t look back. Here was a Starbucks; she went inside and sat down at a table. When her heart stopped racing she went to the loo and splashed water on her face, fixed her make-up. She scrutinised her reflection. It had not passed the test. She was changed, but apparently not changed enough; Julia had seen her twin underneath the difference. Did Julia know? If she knew, why hadn’t she chased after her; why did she look so uncertain? Elspeth visualised Julia’s face: so thin, so tired. She leaned over the sink, braced her arms against it and hung her head. Her chin rested on her chest, and her belly swelled like a red balloon between her arms. Elspeth began to weep, and once she had begun she could not stop. The little fur capelet was wet with her tears.

When she finally emerged from the loo, three women were standing in the queue and they each gave her a dirty look as she passed. Elspeth decided to skip her remaining errands. She ducked into the tube and exited twenty minutes later at King’s Cross St Pancras. She was standing on the doorstep of the tiny flat fumbling for her key when Robert opened the door.

“Where have you been?” he said. “I was almost worried.”

“We have to leave London, Robert. I saw Julia.”

“Did she see you?”

Elspeth told him. “I don’t think she was sure. But she was confused, and she frightened me. We have to leave.”

They were sitting in their squalid kitchen. Elspeth sat at the table with her elbows on it and her head propped in her hands, and Robert paced. The kitchen was so small that he could only move a few steps in each direction. It made her nervous. It reminded her of Julia. “Please don’t do that.”

Robert sat down. “Where can we go?”

“America. Australia. Paris.”

“You don’t even have a valid passport, Elspeth. We can’t get on an international flight.”

“East Sussex.”

Robert said, “Why Sussex?”

“It’s pretty. We could live in Lewes and walk on the Downs every Sunday afternoon. Why not?”

“We don’t know anyone there.”

“Precisely.”

Robert got up and began pacing again, forgetting that Elspeth had just asked him not to do this. “Maybe we should confess. Then we could live in my flat, and eventually things would be normal again.”

Elspeth just looked at him. You are barking mad. After a moment Robert said, “I suppose not.”

“We could get a little cottage. You could finish your thesis.”

“How the hell am I supposed to finish my thesis when I can’t go to the cemetery?” he yelled.

“Why can’t you go to the cemetery?” Elspeth asked quietly. She felt the baby kick.

“Jessica saw you,” he said. “What am I supposed to tell her?”

Elspeth frowned. “Tell her as much of the truth as you can. And let her sort it out. There’s no reason to lie, just omit a few things.”

Robert stood looking down at her upturned face, her borrowed face. That’s how you do it, he thought. I never realised it before. “How long have you been plotting to move to Sussex?” he asked her.

She said, “Oh, since we were tiny. Our parents used to take us to Glyndebourne, and we’d get off the train at Lewes with all the other people in fancy dress. I always wanted to live out in the countryside, there. Actually, I wanted to live in the opera house, but I don’t imagine that’s practicable.”

“Oh, I don’t know,” said Robert, irritably. “It seems to me if you can come back from the dead you could probably live anywhere you like.”

“Well, we can’t live in your flat,” said Elspeth.

“No.”

“Right, then,” said Elspeth. “Can we at least go and look at East Sussex? With an estate agent?”

“Fine,” said Robert. He scooped his keys off the table and grabbed his jacket.

“Where are you going?”

“Out.” He turned to look at her as he put his jacket on; she had a chastened expression he could not remember ever seeing before. “To the library,” he said, softening. “I ordered some books.”

“See you later?” she said, as though she wasn’t quite sure.

“Yeah.”

As Robert walked along Euston Road in the sunshine he thought, I have to talk to Jessica. As he entered the library he thought, I can’t imagine leaving London. He put his things in a locker and went upstairs. What am I going to do? He was sitting and waiting for his desk light to activate when the answer came to him, and he laughed out loud at the obviousness of it.

Robert and Jessica sat in her office with the door closed. It was after hours; all the cemetery staff had gone home. He had told her everything, as best he could. He had tried to place all the evidence before her; he had not spared himself. Jessica listened impassively. She sat in the waning light with her fingers steepled, leaning forward, regarding him with serious eyes. Finally he was silent. Jessica reached out and pulled the little chain of her desk lamp, creating a small pool of yellow light that did not reach either of them. He waited for her to speak.

“Poor Robert,” she said. “It’s all very unfortunate. But I suppose you could say that you got what you wished for.”

“That’s the worst punishment,” Robert said. “I would undo everything, if I could.”

“Yes,” she said. “But you can’t.”

“No, I can’t.” He sighed. “I’d better go. We’re leaving tomorrow. There’s still packing to do.”

They stood up. She said, “Will you come back?”

“I hope so.” He turned on the overhead light and followed her slowly down the stairs. When they were standing at the cemetery gates she said, “Goodbye, Robert.” He kissed her on both cheeks, slipped through the gates and walked away. There he goes, she thought. Jessica watched until Robert disappeared from her sight. Then she locked the gate and stood in the dark courtyard, listening to the wind and marvelling at human folly.