"Let's go and see," Mr Cantor said in a voice which suddenly seemed quite different from his Keep View voice and they both turned obediently.

They walked a pace or two ahead of him down the unknown track but stopped when he said suddenly, "That man... That sheep farmer you know and went to warn last night. What's his name?"

"Alan Denton," Dickie said.

"Yes, of course. A.D."

And just when they both realized that the dead sheep was probably one of those stolen from Alan, they all heard again, quite clearly, the bleating of sheep, followed by Macbeth's excited bark.

Mr Cantor cocked his head and smiled grimly.

"Buck up, kids," he said briskly. "Find that wonder dog of yours and the sheep he's found. Go on! Don't stand there gaping at me... Or let me get in front. I think maybe I'd better."

They were both staring at him in astonishment, for suddenly the Mr Cantor they had known had disappeared and in some miraculous way a stranger had taken his place. They had no time to decide whether they liked this stranger or not, but he seemed to have a mind of his own so they turned and dashed up the track so that they should be the first to share Macbeth's new discovery.

They stopped short at the edge of a flat circle of grass which had been trodden and soiled by sheep. At the far side of the little clearing Macbeth was standing before a hurdle intertwined with bracken and heather and barking furiously.

Mr Cantor joined the twins and stood still looking keenly about him while Mary dashed forward and picked up the protesting little dog.

"Look!" she called over her shoulder. "There's millions of sheep in here. Somebody has made a roof of these hurdle things and covered it all over with heather. It's all disguised and secret. Isn't Mackie a clever little darling to find it?"

"He is," Mr Cantor said quite grimly. "He certainly is. I shouldn't be surprised if he doesn't get a medal - and both of you, too!"

"I think we've found the stolen sheep, haven't we, Mr Cantor?" Dickie asked. "It's lucky we came to Offa's Dyke, isn't it? I s'pose we should go back and tell that policeman."

"I think so, Dickie," Mr Cantor said solemnly. "I think perhaps it's time the police knew all about this. Come on."

The next half-hour was a nightmare to the twins. Within five minutes they were too tired to protest and could only follow Mr Cantor as he trotted back the way they had come.