Jaeger’s hands went to his waist. It was true. He was too fat. “I’ll stay. I’ll think of something. You two get out.”

“No.” This was turning into a farce. March took the envelope from his pocket and pressed it into Charlie’s hand. Take this. We may be searched.”

“And you?” She had her stupid shoes in one hand, was already mounting the chair.

“Wait until you hear from me. Tell nobody.” He grabbed her, locked his hands just below her knees, and threw. She was so light, he could have wept.

The SS were in the basement. Along the passage — the crash of doors flung open.

March swung the grating back into place and kicked away the chair.

The grey BMW drove south down Saarland Strasse, past the slumbering hotels and deserted shops of central Berlin. At the dark mass of the Museum fur Volkerkunde it turned left, into Prinz-Albrecht Strasse, towards the headquarters of the Gestapo.

There was a hierarchy in cars, as in everything. The Orpo were stuck with tinny Opels. The Kripo had Volkswagens — four-door versions of the original KdF-wagen, the round-backed workers” car which had been stamped out by the million at the Fallersleben works. But the Gestapo were smarter. They drove BMW 1800s -sinister boxes with growling, souped-up engines and dull grey bodywork.

Sitting in the back seat next to Max Jaeger, March kept his eyes on the man who had arrested them, the commander of the raid on Stuckart’s apartment. When they had been led up from the basement into the foyer he had given them an immaculate Fuhrer-salute. “Sturmbannfuhrer Karl Krebs, Gestapo!” That had meant nothing to March. It was only now, in the BMW, in profile, that he recognised him. Krebs was one of the two SS officers who had been with Globus at Buhler’s villa.

He was about thirty years old with an angular, intelligent face, and without the uniform he could have been anything — a lawyer, a banker, a eugenicist, an executioner. That was how it was with young men of his age. They had come off an assembly line of Pimpf, Hitler Youth, National Service and Strength-Through-Joy. They had heard the same speeches, read the same slogans, eaten the same one-pot meals in aid of Winter Relief. They were the regime’s workhorses, had known no authority but the Party, and were as reliable and commonplace as the Kripo’s Volkswagens.

The car drew up and almost at once Krebs was on the pavement, opening the door. “This way, gentlemen. Please.”

March hauled himself out and looked down the street. Krebs might be as polite as a scoutmaster, but ten metres back, the doors of a second BMW were opening even before it stopped and armed plain-clothes men were emerging. That was how it had been since their discovery at Fritz-Todt Platz. No rifle-butts in the belly, no oaths, no handcuffs. Just a telephone call to headquarters, followed by a quiet request to “discuss these matters further”. Krebs had also asked them to surrender their weapons. Polite, but behind the politeness, always, the threat.

Gestapo headquarters were in a grand, five-storey Wilhelmine construction that faced north and never saw the sun. Years ago, in the days of the Weimar Republic, the museum-like building had housed the Berlin School of Arts. When the secret police took over, the students had been forced to burn their modernist paintings in the courtyard. Tonight, the high windows were shielded by thick net curtains, a precaution against terrorist attack. Behind the gauze, as if in fog, chandeliers burned.

March had made it a policy in life never to cross the threshold, and until this night he had succeeded. Three stone steps ran up into an entrance hall. More steps, and then a large, vaulted foyer: a red carpet on a stone floor, the hollow resonance of a cathedral. It was busy. The early hours of the morning were always busy for the Gestapo. From the depths of the building came the muffled echo of bells ringing, footsteps, a whistle, a shout. A fat man in the uniform of an Obersturmfuhrer picked his nose and regarded them without interest.

They walked on, down a corridor lined with swastikas and marble busts of the Party leadership — Goring, Goebbels, Bormann, Frank, Ley and the rest — modelled after Roman senators. March could hear the plainclothes guards following. He glanced at Jaeger, but Max was staring fixedly ahead, jaw clenched.

More stairs, another passage. The carpet had given way to linoleum. The walls were dingy. March guessed they were somewhere near the back of the building, on the second floor.

“If you would wait here,” said Krebs. He opened a stout wooden door. Neon stuttered into life. He stood aside to allow them to file in. “Coffee?”

“Thank you.”

And he was gone. As the door closed, March saw one of the guards, arms folded, take up station in the corridor outside. He half-expected to hear a key turn in the lock, but there was no sound.

They had been put in some sort of interview room. A rough wooden table stood in the centre of the floor, one chair either side of it, half a dozen others pushed up against the walls. There was a small window. Opposite it was a reproduction of Josef Vietze’s portrait of Reinhard Heydrich in a cheap plastic frame. On the floor were small brown stains which looked to March like dried blood.

PRINZ-ALBRECHT STRASSE was Germany’s black heart, as famous as the Avenue of Victory and the Great Hall, but without the tourist coaches. At number eight: the Gestapo. At number nine: Heydrich’s personal headquarters. Around the corner: the Prinz-Albrecht Palace itself, headquarters of the SD, the Party’s intelligence service. A complex of underground passages linked the three.

Jaeger muttered something and collapsed into a chair. March could think of nothing adequate to say so he looked out of the window. It commanded a clear view of the palace grounds running behind the Gestapo building — the dark clumps of the bushes, the ink-pool of the lawn, the skeletal branches of the limes raised in claws against the sky. Away to the right, lit up through the bare trees, was the concrete and glass cube of the Europa-Haus, built in the 1920s by the Jewish architect Mendelsohn. The Party had allowed it to stand as a monument to his “pygmy imagination’: dropped among Speer’s granite monoliths, it was just a toy. March could remember a Sunday afternoon tea with Pili in its roof-garden restaurant. Ginger beer and Obsttorte mit Sahne, the little brass band playing-what else? -selections from The Merry Widow, the elderly women with their elaborate Sunday hats, their little fingers crooked over the bone china.

Most were careful not to look at the black buildings beyond the trees. For others, the proximity of Prinz-Albrecht Strasse seemed to provide a frisson of excitement, like picnicking next to a prison. Down in the cellar the Gestapo was licensed to practise what the Ministry of Justice called “heightened interrogation”. The rules had been drawn up by civilised men in warm offices and they stipulated the presence of a doctor. There had been a conversation in Werderscher Markt a few weeks ago. Someone had heard a rumour about the torturers” latest trick: a thin glass catheter inserted into the suspect’s penis, then snapped.

Strings are playing

Hear them saying

“I love you…”

He shook his head, pinched the bridge of his nose, tried to clear his mind. Think. He had left a paper-trail of clues, any one of which would have been enough to lead the Gestapo to Stuckart’s apartment. He had requested Stuckart’s file. He had discussed the case with Fiebes. He had rung Luther’s home. He had gone looking for Charlotte Maguire.