“The fellow undoubtedly acted as a spy, for I once caught him at it.  But spying alone would have been of no use, for there was nothing at any time said that would have brought harm upon them.  They simply discussed what thousands of other people have discussed, the measures that should be taken on behalf of the Stuarts, if one of them came over from France supported by a French force.  The fellow, however, swore that the object of these meetings was to arrange for an assassination of William.  He gave full details of the supposed plot, and in order to give substance to his statements, he hid, in a cabinet of my father’s, a number of compromising papers, professing to be letters from abroad.

“These were found by the officers sent to arrest my father.  He and his five friends managed to escape, but their estates were forfeited.  Of course, what we want to prove is the connection between this spy and his employer, who, for his services in bringing this supposed plot to light, received as a reward my father’s estates.  There is no way of doing this, unless this man can be brought to confess his own villainy in the matter of the letters, and to denounce the scoundrel whose agent he was.  Probably, by this time, he has got nearly all he can expect from his employer, and will at least feel no scruples in exposing him, if by so doing he can save his own neck.

“Now, we have not only discovered the man, but have found out that he is a notorious highwayman, and the leader of a gang; but more, I have found out the day and hour on which he proposes to stop and rob the North coach.”

“Well, Mr. Carstairs, if you have done that,” the man said, “you have done marvels.  That you should find the man might be a piece of good luck, but that you should have learned all this about him seems to me wonderful.”

“It was a lucky accident, altogether.  We saw him, watched him, and managed to overhear a conversation from which we gathered these facts.  It was all simple enough.  Of course, our idea is that we should, if possible, catch him in the act of robbing the coach, bind and take charge of him, saying that we should hand him over to justice, when the coachman and passengers would, of course, appear to testify against him.  Instead of doing this, we should take him somewhere, and then give him the option of either making a clean breast of the whole story, and remaining in our custody until called upon to testify to his statement in a court of justice, whenever required; or of being handed over to the authorities, to be tried and hung as a highwayman.

“One of our greatest difficulties is how to effect his capture.  The attack will be made at night on the coach, and in the darkness we might shoot him, or he might get away.  He is at present in London, at a lodging in a street behind the Abbey, where, doubtless, his real profession is altogether unsuspected by the people of the house.

“Now you know the whole affair.  Let us have your opinion as to the manner in which we had best set about the business.”