''Tworn't a bad notion,' agreed Chippy. 'We'll leg it a bit again, an' then 'ave a look at it.' The boys ran for a mile or more, and then fell into a walk. The blackened strip of country was now out of sight, and they looked round for a place to halt for a few minutes to get their breath and examine the boot. 'We want a place,' said Dick, 'where there's good cover for ourselves, and a clear space all round so that no one can surprise us. I learned that from "Aids to Scouting."' 'I see,' said Chippy. 'Wot about that patch o' thick stuff right ahead?' 'That'll do,' said Dick; 'there's plenty of room all round it;' and the boys ran to the covert and crept into it. 'Now for the boot,' murmured Dick eagerly, as Chippy laid it down between them. 'Here you are, Chippy. Here's my pocket-knife, and there's a screw-driver in it.' 'Righto,' said the Raven. 'I was just a-thinkin' 'ow to open it.' Chippy went to work with the screw-driver in Dick's knife, and in two minutes the heel-plate was off. The screws held the iron tip and a single thickness of leather in place as a cover on the rest of the heel. In the thickness of the heel was a small cavity out of which fell three closely folded scraps of paper. The boys opened the papers and looked at them. They could make nothing of the marks and signs with which the tiny sheets were covered. 'There don't seem no sense at all here,' remarked Chippy. 'Those are secret signs,' replied Dick, 'so that no one can understand the information except the people for whom it is meant. I expect they'd know fast enough, if once they got hold of it.' 'Well, they won't 'ave it this time,' said Chippy. 'Wot are we goin' to do wi' this?' 'I wonder where that sergeant is,' said Dick. 'I'll be bound that was his business on the heath, Chippy--not trying to keep convicts in, but trying to keep spies out.' 'I never took it in when he was tellin' us to tek' care o' the convic's,' said Chippy. 'Not but wot I thought at fust as one of 'em had got away.' 'So did I,' agreed Dick. 'I felt certain it was an escaped convict.' 'An' it wor' Albert,' murmured Chippy in wonder. 'Albert, wot 'ad been bad, an' come down from Lunnon for his health,' and Chippy chuckled dryly. Before the papers were restored and the heel fastened up, Dick measured the hidden cavity with his thumb-nail. It was one inch and a quarter in length, one inch in breadth, and half an inch deep. 'Plenty of room for a lot of dangerous information there,' remarked Dick. 'What makes 'em so sharp on this game?' asked Chippy. 'Oh,' cried Dick, 'I've heard about that. A spy gets a great sum of money if he can carry back full information about the forts and soldiers of another country. You see, it is a great help if you are going to war with that country. You know just what you've got to meet, and you can be ready to meet it.'