The passengers were still up at the pub and if Dr Natouche had returned he had not come below. The Tretheways were sitting in a family huddle near the bar. Out in the darkling landscape the Creeper rose stealthily and police constables patrolled the exits from Ramsdyke into the main roads and the tow-path near the Zodiac.

The cabin, of course, had been swept out and the berth stripped of its bed-clothes. The Hewsons had made use of it not only for their purchases but for their camera equipment and some of their luggage.

Alleyn found that their cameras—they had three—were loaded with partially used film. They were expensive models, one of them being equipped with a phenomenally powerful lens of the sort used by geologists when recording rock-faces.

Their booty from Tollardwark was bestowed along the floor, most of it in a beer-carton; the prints and scraps had been re-rolled, pretty roughly, into a bundle tied up with the original string.

The painting of Ramsdyke Lock was laid between sheets of newspaper in an empty suitcase.

He took it out and put it on the bunk.

Troy and Caley Bard had made a fairly thorough job of their cleaning and oiling but there were still some signs of dirt caught under the edge of brush strokes, but not, he thought, incorporated in the paint. It was a glowing picture and as Troy had said, it was well-painted. Alleyn was not an expert in picture forgery but he knew that the processes were refined, elaborate and highly scientific, involving in the case of seventeenth-century reproductions the use of specially manufactured pigments, of phenolformaldehyde and an essential oil, of baking and of old paintings scraped down to the ground layer. With nineteenth-century forgeries these techniques might not be necessary. Alleyn knew that extremely indifferent forgeries had deceived the widows and close associates of celebrated painters and even tolerable authorities. He had heard talk of ‘studio sweepings’ and arguments that not every casual, unsigned authentic sketch bore the over-all painterly ‘signature’ of the master. One much-practised trick, of course, was to paint the forgery over an old work. An X-ray would show if this had been done.

Outside, presenting itself for comparison, was the subject of the picture: Ramsdyke Lock, the pond, the ford, the winding lane, the hazy distance. Nothing could be handier, he thought, and he did in fact compare them.

He made an interesting discovery.

The trees in the picture were in the right places, they were elms, they enclosed the middle-distance just as the real elms did in the now darkling landscape outside. Undoubtedly, it was a picture of Ramsdyke Lock.

But they were not precisely the same elms.