“He’s too young to have a family to feed. Unless it’s his mother he’s supporting. There may be brothers and sisters younger than he is.”

“As to that, sir, we’d only be guessing. But he’s killed twice now.”

One of the constables searching along the path looked up and called, “Here, sir!”

Walker and Rutledge hurried to where he was standing.

“A man’s coat button, sir,” he said, pointing it out.

“Anyone walking along here could have lost it,” the sergeant told him. “But we’ll have it anyway. In case.”

Rutledge took it from the constable’s hand. It was a very ordinary button, dark brown and with four holes in it. For a coat, as the constable had said. Remembering the drawers of buttons to choose from in the tailor’s shop, he said, “You’re right. It would be hard to prove either way. But we might be lucky.”

On the river a boat swept by, and bursts of laughter carried over the water.

“Where’s this witness you spoke of?”

“A constable took him along for a bite to eat. The man looked half starved.”

“How much did he see?”

“He said he was coming from the direction of the Abbey, walking toward the bridge, when he heard something that sounded like someone choking. He turned toward the sound in time to see one man falling down and another bending over him, as if trying to help. But then he saw that the second man was rifling the pockets of the first, and he shouted for him to stop. The second man turned and stared at him for several seconds, then turned and ran. By the time our witness reached the victim, he was dying. But there was nothing anyone could do. The witness stayed with him, then saw a motorcar on the road, coming toward the bridge, and shouted for help.”

“And you’re certain this witness wasn’t the killer?”

“He was in the clear. He needn’t have hailed the motorcar. And he’d made an effort to staunch the bleeding.”

“Yes, you’re right, it sounds as if he’s exactly what he claims to be.”

Walker was looking toward the road. “Here he comes now, sir. With the constable.”

Rutledge turned. The constable was walking beside a vagrant, a man in shabby clothes, unshaven and thin. He moved with a limp, as if footsore, his eyes cast down, as if searching the pavement for lost coins.

Rutledge went to meet them and greeted the constable before speaking to his companion.

“I understand you witnessed what happened here last night?”

“I did. It was murder, right enough. There were two men, struggling together, and one fell. The other knelt beside him, and I thought at first he was trying to help. But then I saw he was going through the other man’s pockets. He ran as I came up.” The man’s voice was rough, a workingman’s accent.

“Did you get a good look at the one who ran away?” Rutledge asked.

“It was too dark. But he ran like a young person. Quick, and with ease. I thought he must be wearing padded shoes. He made almost no sound.”