When at last they were sitting down to supper Peter asked where Mr Cantor was, and Agnes explained that he had his meal upstairs in his room some time ago. As soon as she had closed the door behind her Dickie clapped his hand to his head and cried out as if in pain. Neither David nor Mary looked up from their soup, but the latter said:

"Don't worry, anyone. He's got an idea and I bet it's a big one. What is it, Dickie?"

Dickie looked round the table triumphantly.

"I bet you'd all like to know who was riding that bike up there on the moor, wouldn't you? I bet I know who it was. Here, Mary. Just come exploring with me and we'll prove it and be back in a sec."

The others got on with their meal without much comment when the twins had gone, but David did say: "Dickie must be on to something if he's left his supper."

Suddenly the door burst open to disclose the twins.

"What did we tell you...?" Mary began, but Dickie stopped her with a dramatic gesture and closed the door behind them.

"What did we tell you?" Mary went on. "We've done it again for the Lone Piners - you can't do without us. Now listen! That bike with the rattling bell that the spy escaped on is Mr Cantor's."

There was a long pause and then knives and forks clattered on to plates as the others stared at them in amazement.

Then, "Don't be ridiculous!" Penny said. "You two are trying to be funny again. How can you possibly know that? He's not the sort of man to have a bicycle."

"Go on, Dickie," Peter said quietly. "Tell us how you know,"

Dickie spoke soberly now.

"I'll tell you. This morning after we'd been for a walk with Mackie we explored round the back here. There's a sort of garden and a shed with all sorts of things in it. There was a man's bike in there and it had a label on the handlebars, addressed to Mr Cantor here. We had a look at the bike and I noticed that the bell was loose and rattled... The bike is there now though in a different place, but the bell still rattles and we bet that man on that bike was Mr Cantor spying on us - or up to some dirty trick."

7. That Van Again

As soon as supper was cleared away they gathered round the fire and began to discuss the day's adventures. Nothing that the elder ones could say could make Dickie change his mind about Mr Cantor,