“Where?” said the sergeant in obvious surprise.

“Llyn-dhu, the Black Lake. It’s not far from here.”

The sergeant grinned.

“You’re not pulling my leg, are you?”

“No, said Susan, were not—promise!”

“Then somebody must be pulling yours, because there’s no such place of that name round here that I know of, and!”ve been at Wilmslow all of nine years. Sounds more Welsh than anything.”

Colin and Susan were so taken aback that, for a moment, they could not speak.

“But we saw it from Castle Rock less than an hour ago!” said Susan, and tears of exasperation pricked her eyes. “Well we didn’t really see it. because it was covered in mist, but we know it’s there.”

“Mist, did you say? Ah now perhaps we’re getting somewhere. There’s been fog on Lindow Common for days, and the only lake in the district is there. Do you think that’s what you want?”

“Llyn-dhu, Lindow: it could be: it had to be!”

“Ye-es; yes, that’s it,” said Colin. We must have got the name wrong. Is it far?”

They followed the sergeant’s directions, and after a mile came upon an expanse of damp ground, covered with scrub, and heather, and puddles. A little way off the road was a notice board which stated that this was Lindow Common, and that cycling was prohibited. And in the middle of the common was a long lake of black peat-stained water.

The children stood on the slimy shore. The air was dank and the scenery depressing. The common was encircled by a broken rash of houses, such as may be seen, like a ring of pink scum, on the outskirts of most of our towns and villages today.

“Garlanded with mosses and mean dwellings.” Fenodyree’s words came back to the children as they looked at the brick-pocked landscape. But what was most obviously wrong was that they could see all this. For if they were indeed at Llyn-dhu, then, within the space of an hour, it had rid itself of every trace of the mist that had shrouded it for the last ten days.