In the far corner of the room there was an illuminated fish tank, multicoloured tropical fish zigzagging through a meticulously recreated seabed, air bubbling constantly up through the water from an oxygen feed. Tins of fish feed were stacked on a small table beside it. Li picked one up. It was half full. He sprinkled some feed on the water and watched the fish peck at it in desultory fashion as it fell slowly to the bottom of the tank. He wandered out on to the glassed balcony. It was north-facing, so no hotter than the rest of the house. There were two comfortable armchairs and a low table with a single, empty bottle of beer on it, an ashtray with half a dozen cigarette ends and a pack of Marlboro cigarettes. Li picked up the pack. There were ten or more cigarettes still in it. He replaced it on the table. With the angle at which the light was striking the bottle, he could see smears of greasy fingerprints all over the dark glass. It was strange, he thought, how dead people left physical traces behind them long after they were gone. This apartment would be filled with vestiges of the oily residue left by Chao Heng’s fingers on everything he touched. A touch that was uniquely his. Or hair gathered in the drainer in the sink and the bath, caught on combs and brushes. The fine dust of his dead skin shed over years would lie like a hidden snow among the fibres of the carpet and the bed, and in ledges along undusted surfaces. His scent would linger in the weave of the clothes that hung in the wardrobes. His personality, in all its diversity, reflected in his choice of lifestyle, clothes, furniture, and in the books he read. All of these were clues, not necessarily to the murder, but to the man. And knowing the man was an important step towards knowing his killer.

From the balcony, Li looked down into the compound below. He could see the three police vehicles and the gate in the high wall that led in from the street. He closed his eyes and pictured the killer carrying Chao’s prostrate form over his shoulder between the door of the apartment block and the nearest parking point. It was about fifteen feet. He opened his eyes and checked the streetlights. They were few and far between, and the trees would cast dense shadows. But there would be a light over the main entrance and it would have illuminated those fifteen feet, making it the highest risk point of the journey from the apartment to the park. And that after carrying Chao down five flights of stairs, unlocking and then locking the stair gate behind him again. His killer was not only a very determined man, but he was strong and fit.

“Qian,” he called.

Qian came on to the balcony. “Yes, boss?”