“I beg your pardon, Mr. Blake,” said the Sergeant.  “I was just going to send word by your servant that I wanted to speak to you.  There isn’t a doubt on my mind that this boy—­this most meritorious boy,” added the Sergeant, patting Gooseberry on the head, “has followed the right man.  Precious time has been lost, sir, through your unfortunately not being at home at half past ten last night.  The only thing to do, now, is to send for a cab immediately.”

In five minutes more, Sergeant Cuff and I (with Gooseberry on the box to guide the driver) were on our way eastward, towards the City.

“One of these days,” said the Sergeant, pointing through the front window of the cab, “that boy will do great things in my late profession.  He is the brightest and cleverest little chap I have met with, for many a long year past.  You shall hear the substance, Mr. Blake, of what he told me while you were out of the room.  You were present, I think, when he mentioned that he held on behind the cab, and ran after it?”

“Yes.”

“Well, sir, the cab went from Lombard Street to the Tower Wharf.  The sailor with the black beard got out, and spoke to the steward of the Rotterdam steamboat, which was to start next morning.  He asked if he could be allowed to go on board at once, and sleep in his berth over-night.  The steward said, No.  The cabins, and berths, and bedding were all to have a thorough cleaning that evening, and no passenger could be allowed to come on board, before the morning.  The sailor turned round, and left the wharf.  When he got into the street again, the boy noticed for the first time, a man dressed like a respectable mechanic, walking on the opposite side of the road, and apparently keeping the sailor in view.  The sailor stopped at an eating-house in the neighbourhood, and went in.  The boy—­not being able to make up his mind, at the moment—­hung about among some other boys, staring at the good things in the eating-house window.  He noticed the mechanic waiting, as he himself was waiting—­but still on the opposite side of the street.  After a minute, a cab came by slowly, and stopped where the mechanic was standing.  The boy could only see plainly one person in the cab, who leaned forward at the window to speak to the mechanic.  He described that person, Mr. Blake, without any prompting from me, as having a dark face, like the face of an Indian.”

It was plain, by this time, that Mr. Bruff and I had made another mistake.  The sailor with the black beard was clearly not a spy in the service of the Indian conspiracy.  Was he, by any possibility, the man who had got the Diamond?

“After a little,” pursued the Sergeant, “the cab moved on slowly down the street.  The mechanic crossed the road, and went into the eating-house.  The boy waited outside till he was hungry and tired—­and then went into the eating-house, in his turn.  He had a shilling in his pocket; and he dined sumptuously, he tells me, on a black-pudding, an eel-pie, and a bottle of ginger-beer.  What can a boy not digest?  The substance in question has never been found yet.”