She opened her eyes immediately, or so she thought. She had not realised how tired she was. Her brain was still not keyed to Beijing time. She looked at her watch and realised with a shock that she had just lost twenty minutes. She blinked and tried to make her mind focus on something. The cigarette ends. There was a pack of cigarettes lying on the desk. She picked it up and took one out. The tobacco had a strong, bitter, toasty smell. It made her think of coffee stewing on a hot plate. She examined the pale pattern on the cork-coloured tip, the brand name red on white just above it. A single cigarette end at each crime scene. Smoked by the same man. What was it that was so wrong about that? She knew, of course. No professional would be so careless. And yet they were professional killings. And then suddenly she had a revelation, and sat forward in the chair, heart pounding. It had only been obscure because it was so obvious.

The sound of voices came through from the outer office as the detectives returned from their meeting. Li appeared in the doorway.

“I’ve just had a revelation,” she said.

“You hungry?” he asked, as if he hadn’t heard.

She hadn’t thought about it, but now that she did she realised that her stomach was growling. “Sure. Listen, this is important.”

“Good. I haven’t eaten all day. We’ll get something at the stall on the corner, and then I’m going to the Ministry of Agriculture. If you want to come . . .”

“Try keeping me away.” She stood up. “Li Yan . . . Are you going to hear me out or what?”

He held the door open for her. “Tell me on the way.” But, as he turned, the chain on his fob watch caught on the handle and broke. “Damn!”

She looked at the chain. “It’s just a broken link. It’s fixable.”

“Later.” He slipped it off his belt and dropped it into the top drawer of his desk. He saw she was wearing a wristwatch and tapped his own wrist. “You can keep me right.”

By the time they were out in the corridor she was having trouble keeping up with him. He seemed infused with a fresh energy and new determination. “I just put a stop to wasting any further time on trying to make some futile drugs connection. At least it’ll cut down on the paperwork.”

“Li Yan . . . The cigarette ends . . .”

“What about them?”

They were on the stairs now. “I think I know why he left one at each crime scene.”

Li stopped. “Why?”

“Because he wanted you to find them. He wanted you to make the connection.”

“Why?” Li asked again.