‘Shut up!’ he snarled; some part of him, the part that wasn’t focused on panicking, managing to register surprise at the violence in his tone. He must have surprised Theo too, because miraculously, it worked. The rebellion stopped immediately and she clutched his coat tighter.

They went on and on for what seemed like forever. Albert had a shooting pain in his calves, his chest was burning and his arms were getting heavier and heavier. Just when he thought he couldn’t take it any more, the passageway ended and they entered a large cavern, hewn out of the rock, bathed in the same eerie glow as the tunnel. It was a huge, sprawling space, roughly oval in shape, stretching at least a hundred metres in every direction from the centre. On the right, there was another tunnel—whether it led out or in was impossible to say—on the left were two more. He couldn’t tell if it was natural—and he didn’t care. It could have been built by giant intelligent earthworms as part of a wind tunnel experiment for all it mattered.

He half released, half dropped Theo to the floor and stood, doubled over, drawing deep, heaving breaths, his chest on fire.

He’d barely had time to pant a bit when he heard feet pounding in the tunnel behind him and he had to move hurriedly out of the way. Ollie burst through, arms pumping, moving faster than one would have imagined possible for a man his size, and stopped just inside the entrance, smiling. He looked remarkably fresh, as if he’d just been for an enjoyable early morning stroll down the tunnel, not even sweating.

June looked at him, the worry lines on her face visible even in the dim cavern. ‘Where are they?’

‘Oh, they’ll be a while yet,’ he said. ‘One of their deadeyes shot the front of the tunnel closed. Lucky the whole roof didn’t come down. They’ll get through or find another way in, never fear, but not for a bit.’

So that was the rumbling sound he had heard.

Ollie, in the meanwhile, was looking at them expectantly, like an edubot taking attendance in class. ‘All here?’ he asked.

Albert did a quick head count. All his companions of the night’s journey were present and accounted for, as was one of the Outliers, the one who had recognized the bum outside. The rest were missing, having fled into different pipes. Even as he did the math, two more burst into the cavern from another tunnel and scurried over to join them.

‘Zain isn’t here.’ said the man standing with them.

‘I saw Zain,’ chipped in one of the Outliers. ‘’E took the F tunnel. It’s a dead end, cap’n.’

The first man scowled, a frown creasing his dark forehead. ‘Gavin, Willis and Rashid are missing, too,’ he said.