Cooler said, ‘Oh, that old story. I’m afraid you are riled at me, Mr Martins. Look at it this way – you as a citizen, owing allegiance –’

‘The police have dug up the body. They’ll be after you and Winkler. I want you to warn Harry …’

‘I don’t understand.’

‘Oh, yes, you do.’ And it was obvious that he did. Martins left him abruptly. He wanted no more of that kindly humanitarian face.

It only remained then to bait the trap. After studying the map of the sewer system I came to the conclusion that a café anywhere near the main entrance of the great sewer, which was placed like all the others in an advertisement kiosk, would be the most likely spot to tempt Lime. He had only to rise once again through the ground, walk fifty yards, bring Martins back with him, and sink again into the obscurity of the sewers. He had no idea that this method of evasion was known to us: he probably knew that one patrol of the sewer police ended before midnight, and the next did not start till two, and so at midnight Martins sat in the little cold café in sight of the kiosk, drinking coffee after coffee. I had lent him a revolver; I had men posted as close to the kiosk as I could, and the sewer police were ready when zero hour struck to close the manholes and start sweeping the sewers inwards from the edge of the city. But I intended, if I could, to catch him before he went underground again. It would save trouble – and risk to Martins. So there, as I say, in the café Martins sat.

The wind had risen again, but it had brought no snow; it came icily off the Danube and in the little grassy square by the café it whipped up the snow like the surf on top of a wave. There was no heating in the café, and Martins sat warming each hand in turn on a cup of ersatz coffee – innumerable cups. There was usually one of my men in the café with him, but I changed them every twenty minutes or so irregularly. More than an hour passed. Martins had long given up hope and so had I, where I waited at the end of a phone several streets away, with a party of the sewer police ready to go down if it became necessary. We were luckier than Martins because we were warm in our great boots up to the thighs and our reefer jackets. One man had a small searchlight about half as big again as a car headlight strapped to his breast, and another man carried a brace of Roman candles. The telephone rang. It was Martins. He said, ‘I’m perishing with cold. It’s a quarter past one. Is there any point in going on with this?’

‘You shouldn’t telephone. You must stay in sight.’