who was causing it and who still, intent and busy, had not the least
idea of the other's proximity.

A faint smile touched Dunn's lips. The situation seemed not to be
without a grim humour, for if one-half of what he suspected were
true, one might as sensibly and safely attempt to break into the
condemned cell at Pentonville Gaol as into this quiet house.

But then, was it perhaps possible that this fellow, working away so
unconcernedly, within arm's-length of him, was in reality one of
them, seeking to obtain admittance in this way for some reason of
his own, some private treachery, it might be, or some dispute? To
Dunn that did not seem likely. More probably the fellow was merely
an ordinary burglar--some local practitioner of the housebreaking
art, perhaps--whose ill-fortune it was to have hit upon this house
to rob without his having the least idea of the nature of the place
he was trying to enter.

"He might prove a useful recruit for them, though," Dunn thought,
and a sudden idea flashed into his mind, vivid and startling.

For one moment he thought intently, weighing in his mind this idea
that had come to him so suddenly. He was not blind to the risks it
involved, but his eager temperament always inclined him to the most
direct and often to the most dangerous course. His mind was made up,
his plan of action decided.

The scratching of the burglar's tool upon the glass ceased. Already
he had smeared treacle over the square of glass he intended to
remove and had covered it with paper so as to be able to take it out