“At first it sounded as if he was trying to force the lock. And then for a time there was nothing. We were just settling down when we could hear him again. I swear it sounded as if he was sliding something under the door. Marshall thought he might be blocking it, but after a bit it smelled as if he was trying to burn his way through. The passage filled with smoke. You can still smell it!”

Walker sniffed the air, then turned to Rutledge. “Do you?”

Rutledge nodded. It was faint, but enough smoke lingered to pick it out, now that it had been brought to his attention. Walker went again to the door and this time opened it. “Inspector? Sir?” he said after a moment, and Rutledge went to see what he’d found.

Charred rags were jammed against the bottom of the door, and Rutledge bent down to touch them. They were still damp, as if they had been lit and then nearly doused, to create a maximum of smoke with a minimum of fire. Rutledge looked up the alley toward the main road, but he couldn’t see Mrs. Sanders’s window. Which meant she couldn’t have seen whoever was at work here.

“He could have set the building on fire,” Walker declared, kicking the rags away from the door, and then squatting beside them to sift through them. But they were torn cloths, something that could have been found in a dustbin or a tip, Rutledge thought, used for cleaning and then discarded.

“I doubt the station would have caught. The outside of the door is blackened but not heavily charred. I think he was intending to stampede your charges.”

Walker got to his feet. “If that’s what he was after, he succeeded. There must have been pandemonium. Nobody relishes the thought of being burned alive.”

“He must have seen you leave with Tom. He knew he was safe.”

Walker looked at Rutledge. “I don’t like the sound of that. That he was watching.” He took a deep breath. “I was of two minds when you wanted these men clapped up. But now they’ll be released, and the two of us can’t watch six of them.”

“But fright may have sharpened their memories. Let’s find out.”

They went back inside and told the anxious men in the holding cell what they’d discovered.

Tuttle, Walker’s nephew, said, “Be damned to him, then. He’s a coward.”

But Marshall disagreed. “My uncle was out in India for a time. He told me that old tigers got a taste for man, when they couldn’t kill larger prey. And they were more dangerous because of that. Their brethren in the jungle would slip away if they got the scent of a person. But not these.”

“He’s not a tiger,” one of the other men said. “He’s mad, that’s what he is.”