“Hard to tell,” said Melody. “If I’m interpreting these readings correctly, and I’d be the first to admit that there’s a whole lot of guesswork involved . . . it seems our Intruder has added a whole new platform to this station. A half-way place, where its world butts up against ours. This new platform comes and goes, not always there, or at least, not always connected to our reality. It’s the Beast’s lair. Home for its new physical form. For whatever shape it’s taken in our world. We can only access this new station with the Intruder’s permission.”

“Is it there now?” said JC.

“Oh yes,” said Melody. “It’s driving my long-range sensors crazy. They don’t like the taste of it at all.”

Kim looked round suddenly. “JC, something’s coming.”

Everyone turned to look at her. JC moved over to stand beside her, but her gaze was elsewhere.

“Are you sure?” said Melody. “There’s nothing on the monitors.”

“Something’s coming,” said Kim, in a dreamy voice. “Something bad.”

JC studied Kim, who was floating in mid air with her head cocked slightly on one side, as though listening to something only she could hear.

“What is it, Kim? What’s coming for us? Where is it coming from?”

Her left hand rose slowly to point at the far tunnel-mouth. Everyone looked into the darkness, but there was no roar of an approaching train, no pressure wave of disturbed air. Even the rail tracks were free of any vibration. Natasha and Erik stood close together. JC and Happy stared silently at the tunnel-mouth, considering their options. And Melody stood protectively between her machines and whatever was coming, her machine-pistol at the ready. Happy surreptitiously dry swallowed a couple of pills. He took a deep breath, and sweat popped out across his face. His heart was beating dangerously fast.

A Tube train emerged from the tunnel-mouth, moving smoothly and silently, an ordinary train, with ordinary empty cars. Except the engine made no sound at all, and the brightly lit cars didn’t rock or clatter in the slightest. The train pulled slowly, steadily, into the station, with barely a breath of disturbed air, and came easily to a halt. The five agents braced themselves, ready for any kind of attack; but nothing happened. After a while, one set of car doors slid silently open and waited, invitingly. No-one moved. None of them liked the look of this train. There was nothing obviously unnatural about it, apart from its quiet, but if anything, it was too ordinary, too perfect, as though it was newly made, never used before.