‘What have they done to you?’ That was the woman. ‘Evil fuckers.’

He liked her, despite the tidal wash of pain, and that was dangerous.

Silver light, growing.

What are they doing?

Grey and black rotating.

Where—?

The torture cell was gone.

TWENTY-ONE

EARTH, 1941 AD

From the pavement of Baker Street, the building was a massive bone-grey cube lined with blacked-out windows. Inside, it was a hive of orthogonality: square-cross-sectioned corridors and cubic interior rooms: windowless, functional and bleak. This was the headquarters of the Special Overseas Executive, home of code-makers rather than breakers, where even the air felt pressurized; and the stay-at-home executives looked even more strained than the agents getting ready to parachute in to some darkened field to be met by resistance fighters or Wehrmacht bullets; because you never knew, sitting at a radio set in London and listening to enciphered dots and dashes, whether the operator over there in Holland or France had been turned – was sending the signal with a Luger against their temple – or was even German, while the person they had replaced now whimpered in a Gestapo cell or rotted with a hundred other corpses in a pit.

But SOE had cells of their own, and that was where the two enemy agents went: down to the basement, under military guard. Gavriela remained somewhere in the core of the building – every floor and corridor looked the same – standing next to two soldiers, while Rupert Forrester went off to chat to a short civilian, or rather someone not in uniform; for everyone here was some kind of soldier, even her.

They’re not going to do anything.

Not to her.

She had no logical grounds for optimism, beyond standing here instead of in a cell like the prisoners; but Rupert had looked at her as a subordinate in need of discipline, not an enemy. Still, she was better at reading codes and ciphers than human beings.

A one-armed man came around the corner and winked at her.

‘Brian!’ She could not understand why he was here rather than Bletchley. ‘What’s going on?’

‘Well, darling Gabby, I’m feeling relieved’ – with a grin – ‘that you’re on our side after all.’

He had never called her darling before. Tonight he looked like a man who had just tilted a massive rucksack off his back, thought that was it, then been given a heavy box to carry, and was trying to make the best of it.

‘The message-within-the-message had a prefix en clair,’ she said, ‘which I happened to recognize. And the rest was a simple monoalphabetic substitution.’

They must have found the decrypt, because of the twenty policemen descending on Trafalgar Square. If they had simply been suspicious of her, there would have been a team of plainclothes watchers, no more. And clearly, from Brian’s words, he had been working with Rupert on this.

‘Really.’

‘You’re going to think I’m insane, Brian. Once I’ve told you how I recognized the prefix, I mean.’

‘That’s a possibility, I guess. But I think you’re sane enough.’

He looked back along the corridor. At the far end, Rupert turned, and for a moment it was like a resonance cavity: some imperative signal bounced back and forth between them, growing stronger. Then Rupert nodded, touched the shoulder of the man beside him, and walked out of sight.

Gavriela wanted to ask about that, and why an SIS officer like Rupert chose to use SOE headquarters, and how long Brian had been watching her; but tonight she had better respond to questions rather than pose them. Curiosity about secret war work, beyond her own remit, could drop her into the kind of trouble she was trying to evade.

He was a friendly interrogator, it turned out.

They used one of the anonymous offices, and she told him quickly what the message said and how she worked through it. He nodded when she mentioned Trafalgar Square and the unknown time, then backtracked.

‘So what are these cryptonyms?’ he said. ‘Eagle and darkness?’

‘I’m guessing that one of the two men in the basement, or wherever you’ve got them, is the eagle. Maybe that’s a tattoo on his forearm, or a design on his tie-clip, or something. For identification. Or maybe that’s too easy, I don’t know. But the darkness … that’s different.’

She was vibrating inside, sick and scared and elated, on the brink of spilling her personal madness.

‘It started when I moved to Zürich,’ she said. ‘Fourteen years ago, on my first day as a student, although it perhaps reinforced the occasional odd perception from childhood. Or maybe you’ll call it hallucination.’

‘Hallucination?’

‘Yes—’

An endless hour later, a knock sounded and the door swung in. Rupert’s face was corpse-white.

‘What is it?’ said Brian.

‘A moment.’ Rupert turned, nodded to someone in the corridor outside, and came in. ‘I’d like to catch up, if that’s OK with you.’

He used his heel to close the door.

‘Gabby can, er, see things other people can’t,’ said Brian. ‘Certain individuals are surrounded by a sort of dark aura—’

‘Not an optical phenomenon.’ Gavriela wanted Rupert to understand. ‘It’s a psychological artefact, like one of those Benham Tops.’

‘Like a what?’

‘Sorry. A spinning-top.’ So much of her knowledge of people came from textbooks. ‘If you spin a certain black-and-white design at the right speed, people see it in vivid colours: red, green, violet. There’s no diffraction or refraction involved. It’s a neurological effect.’

Brian closed his eyes, smiled as he pushed out a breath, then looked at Rupert.

‘See?’ he said. ‘She comes out with nutty stuff and you have to believe her.’

Rupert frowned at nutty, one of those Americanisms he despised.

‘And they’re good at hypnosis,’ Brian went on. ‘Or something like that.’

‘Who is?’ said Rupert.

‘The people with the auras. Possessed of demons, or whatever. The darkness.’

‘And the two men at the rendezvous?’

Gavriela said, ‘They’re both tainted with it. I don’t know whether “possessed” is the right word, but it might be. The intercept I decrypted used the word, so that much is not delusion.’

‘What word?’ asked Rupert.

Brian said, ‘Dunkelheit.’

Then he got up from his chair.

‘Are you all right, Rupe?’

‘Not entirely. Can I–?’ Rupert sat down on what had been Brian’s chair. ‘Look, Gavriela—’

Brian raised his eyebrows. He knew her as Gabby Woods.

‘—are you sure about this hypnosis? In fact, didn’t you have a book on the subject’ – his eyes focused on a remembered image – ‘the night we first met in Oxford?’

‘Someone had left the book in the pub,’ said Gavriela. ‘I took it with the barmaid’s approval. It made partial sense of the things I’d seen … but only partial.’

Rupert rubbed his face, which remained bloodless: white, with the ghost of blue veins.

‘That might explain how thirty minutes ago our German guest got away.’

Time seemed to jump: scratched record, gramophone needle; something like that.

‘Got away?’ said Brian. ‘From this place?’

Perhaps it was the dungeons that had brought Rupert here rather than Broadway Buildings. But Broadway these days was only nominally SIS HQ, so close to Whitehall, that prime Luftwaffe target. The real headquarters was Bletchley Park, SIS squeezed in with GCHQ, plus the Whaddon Hall outstation down the road.

Such knowledge in her head. They would have to be sure about her, to allow her to leave.

‘All right, Gavriela.’ Rupert glanced at Brian, then focused on her again. ‘Gabby. These hypnotists with the auras – or whatever – are Nazis, have I got that right?’

‘I …’ Gavriela stopped. ‘It sounds like one of those serials on the wireless, doesn’t it? But I really don’t know.’