“If we don’t go,” Stephen said, “he’s going to kill people. This is our one and only chance. And we have to decide now.”

Callum exhaled loudly and banged his head against the headrest. In the distance, I could hear the neer-ner-neer-ner-neerner of sirens, police cars chasing a man they could never see, never catch.

“Can’t you call someone?” I said. “Get someone to tell you what to do?”

“There is no one,” Stephen said. “We have superiors, but no one can make this decision. There’s too little time and too little information. It’s up to us.”

He opened the computer once again.

“King William Street station,” he said. “Popular with urban explorers. They have drawings and photos up. Built in 1890, closed in 1900. During the Second World War it was converted into an air raid shelter . . . There are two access points. The main one is in the basement of a large office building called Regis House on King William Street, like the sergeant just said. That leads to the original spiral emergency staircase. You go down seventy-five feet to the tunnels. The other access point is at London Bridge station. The old King William Street tunnels are used for ventilation for that station. The only people who can get down there are London Underground engineers. The public can’t go down there anymore, because it’s full of live cables.”

“My favorite words,” Callum said. “Live cables.”

“You can go in through London Bridge,” Stephen said. “It sounds like you can cross under the Thames through a tunnel. I can go down the steps. We’ll come at him from two directions and get him between us. I’m not saying this is completely safe, or that it’s ideal. But we are quite literally the only people who can stop him, and this is the only time we’ve ever known where he plans to be. We signed up to this job for a reason.”

“Because we’re freaks,” Callum said. “Because we’re unlucky.”

“Because we can do something other people can’t.”

“But they didn’t tell us about this, did they? They didn’t tell us that someone on the last squad went mental and murdered the others.”

“Would you mention that?” Stephen asked simply.

I don’t plan many sieges or raids, but even I know that it’s bad when you are going somewhere through a basement, to a place seventy-five feet underground that most people aren’t even aware of.

“I hate this plan,” Callum finally said. “But I know you’ll go down there alone if I don’t go. So I guess I’m in.”

“I have to go with you,” I said.