He must have raised his voice for the last sentence for Mr Cantor heard it as he opened the door. He smiled at Dickie, who fidgeted uncomfortably, as he said, "I can tell you that, Richard. I was talking about something to eat. That good woman has promised to find us some food."

"She doesn't look good to me," Mary said. "I think she looks like a witch. I bet she puts a spell on us so that we can't move from this place and only a fairy prince can rescue me... P'raps you're a fairy prince in disguise, Mr Cantor?"

Their host looked really startled at this and dropped the pipe he was filling. Dickie dashed over to pick it up, but Mary noticed his strange look at her innocent remark.

They sat, an odd-looking trio, in the fireplace and enjoyed their cold lunch. Mackie had his share too and then lay with his nose on his paws, while Dickie and Mary sipped their hot, strong tea and Mr Cantor puffed his pipe. The flickering firelight glinted on his glasses as he turned to answer Dickie, who said:

"Can we walk along Offa's Dyke this afternoon? Will you show us that, please?"

"Why not indeed?"

So, a little later, they said "Good-bye" to the witch, who actually smiled at the twins and did a sort of curtsey to Mr Cantor who whispered something to her and then slipped a piece of paper into her hand. Both Dickie and Mary were very quiet as they walked on for they had seen him do this and did not like it. Somehow they both began to feel that they were not finding out very much about their victim, who seemed to be too clever for them.

Although he kept on talking as they walked - and everything he said was interesting - they did both notice that Mr Cantor was always looking about him very keenly. Once, after they had left the road and were walking on a track crossing a bare hillside, Mary interrupted him to say:

"What do you keep looking for, Mr Cantor? You're looking on the ground all the time you're talking."

"Arrowheads, my dear. You look too. You wanted one for yourself, didn't you?"

"You don't mind if I don't, do you, sir?" Dickie said. "We can't all be looking on the ground all the time, else we shan't get anywhere."

Soon after this they reached the top of a little hill and paused under two tall fir trees.

"Now," said Mr Cantor, "if I have brought you the right way by the map we should see the dyke from here."

"I see it," Mary said quietly. "It's grand. Look, Dickie!"

North and south of them for as far as they could see stretched the shape of the earthen wall with a deep ditch on the Welsh side that was built by an army of slaves over a thousand years ago.