‘I just had a really bad thought,’ she said. ‘The Wolf. I’ve never heard or read anything about them that didn’t just assume they were a man. Even I did. What if they’re real after all and it’s her, and she’s about to Abraham Lincoln Kosygin?’

‘Then,’ Knox said, feeling the Beretta in the shoulder holster under his jacket, ‘we’re about to face a Soviet super-soldier with one gun between us.’

Anna didn’t understand why people paid so much money just to see what happened onstage at the ballet when the real performance was going on off it. She watched dancers limber up and flow effortlessly from light to darkness, seamstresses make frantic final checks and quick alterations to costumes, and technicians move huge sets and lighting rigs between them, all in near silence and perfect unison, as the music from the orchestra pit blared around them.

It was a smooth, professional production and everyone involved was too focused on what they were doing to notice Anna, wrapped in her black shawl, standing perfectly still in between a brick pillar and a gantry ladder next to one of the rear wing curtains. None of the dancers clad in their leotards covered with hearts, diamonds, clubs, and spades saw her as they dashed past her, and from her little nook she had a perfect, uninterrupted view of the stage itself, the BBC television camera on the far side of the stalls, and, directly above it, Kosygin’s box.

She felt a change in the tone of the movement around her. It was small, as if the dancers and crew were all suddenly concentrating on their jobs just a little more intensely. Anna didn’t know what had prompted this subtle shift, but then when a man dressed in a pink costume emblazoned with symbols from every card suit glided through the dark and stopped barely a foot in front of her in the empty wing she understood: Nureyev had arrived.

Anna was close enough to reach out and touch the great dancer’s lithe, muscled body, and she almost did. But after a brief lull the music rose again and suddenly he was out under the glare of a spotlight, leaping impossibly high in the air as the orchestra reached a crescendo.

With the star delivered to his audience, backstage settled once more into its own quiet choreography, and Anna allowed herself a few more moments to appreciate it. But then she felt another change. Not a subtle elevation of the general tone, but an intrusion, an injection of commotion.

She shrank back further into her crevice as her eyes searched for the cause. Twenty feet from her, on the other side of a group of dancers and a large piece of plywood painted to look like a row of old chimneys, were two people who, like Anna, should not be there.