came plump on the boys as they raced round a bend in the
way, for the two scouts were now following the heath-track where they
had last seen the prints of the soldier's ammunition boots.

'Hooray!' yelled Chippy, who was a little in front. ''Ere he is.
Hooray!' and Dick joined in the cheer.

'You two again!' cried the astonished sergeant. 'What on earth are you
nippers up to?'

'We've discovered a spy, sergeant,' panted Dick. 'He's running after
us. He'll be up in a minute.'

At the word 'spy' the sergeant's face underwent an extraordinary
change. It filled with wonder, and then a grim alertness sprang to
life all over him. He dropped his hand to his holster, and whipped out
a big regulation 455 revolver, blue and sombre. The boys formed behind
as under cover of a tower of strength, and the spy dashed round the
bend.

'Hands up!' bellowed the sergeant, and the spy knew better than to
disobey with that grim dark muzzle laid full on his body.

'Heavenly powers!' murmured the sergeant, 'I was right. As sure as my
name's John Lake I was right. Didn't I see you on the heath just about
here last Thursday?' he demanded of the spy. The latter made no reply.
He stood, drawn up to his full height, his hands above his head, and in
one of them was a long-bladed hunting-knife of the sort which folds
into small compass. Now it was fully opened, and looked a very
dreadful weapon. The man was white as death, and gasping fiercely from
his run and this frightful surprise.

'Drop that knife,' commanded the sergeant, 'or I'll put a bullet
through your wrist.'

The spy's wild eyes were fixed on the English soldier's grim face. He
knew when a man meant what he said, and he dropped the knife.

'Step two yards back,' went on the sergeant. The spy did so.

'One o' you boys pick up that knife,' murmured the sergeant; and Dick
ran and fetched it.

'Now, I'm in the dark yet,' went on the sergeant quietly; 'all this
looks very suspicious, but how do you boys come to reckon you've nabbed
a spy?'

Dick began with the boot and the papers hidden in it.

'That's enough, my lad,' said the sergeant. 'We'll lose no time.
There's plenty o' reason, I can see, to take him in on suspicion, and
after hearing that I'd shoot him at once if he tried to escape. Now
you,' he went on to the spy, 'turn right round and march ahead as I
tell you. And remember I'm a yard behind you with a cocked revolver.
March!'

The spy turned, and w