Mrs. Pett uttered an exclamation.

“And this butler of yours—­Skinner.  Shall I tell you something about him?  You perhaps know that when the big detective agencies, Anderson’s and the others, are approached in the matter of tracing a man who is wanted for anything they sometimes ask the smaller agencies like my own to work in with them.  It saves time and widens the field of operations.  We are very glad to do Anderson’s service, and Anderson’s are big enough to be able to afford to let us do it.  Now, a few days ago, a friend of mine in Anderson’s came to me with a sheaf of photographs, which had been sent to them from London.  Whether some private client in London or from Scotland Yard I do not know.  Nor do I know why the original of the photograph was wanted.  But Anderson’s had been asked to trace him and make a report.  My peculiar gift for remembering faces has enabled me to oblige the Anderson people once or twice before in this way.  I studied the photographs very carefully, and kept two of them for reference.  I have one with me now.”  He felt in his pockets.  “Do you recognise it?”

Mrs. Pett stared at the photograph.  It was the presentment of a stout, good-humoured man of middle-age, whose solemn gaze dwelt on the middle distance in that fixed way which a man achieves only in photographs.

“Skinner!”

“Exactly,” said Mr. Sturgis, taking the photograph from her and putting it back in his pocket.  “I recognised him directly he opened the door to me.”

“But—­but I am almost certain that Skinner is the man who let me in when I called on my sister in London.”

“Almost,” repeated the detective.  “Did you observe him very closely?”

“No.  I suppose I did not.”

“The type is a very common one.  It would be very easy indeed for a clever crook to make himself up as your sister’s butler closely enough to deceive any one who had only seen the original once and for a short time then.  What their game is I could not say at present, but, taking everything into consideration, there can be no doubt whatever that the man who calls himself your nephew and the man who calls himself your sister’s butler are working together, and that Jerry Mitchell is working in with them.  As I say, I cannot tell you what they are after at present, but there is no doubt that your unexpected dismissal of Mitchell must have upset their plans.  That would account for the eagerness to get him back into the house again.”

“Lord Wisbeach thought that they were trying to steal my nephew’s explosive.  Perhaps you have read in the papers that my nephew, Willie Partridge, has completed an explosive which is more powerful than any at present known.  His father—­you have heard of him, of course—­Dwight Partridge.”

Mr. Sturgis nodded.

“His father was working on it at the time of his death, and Willie has gone on with his experiments where he left off.  To-day at lunch he showed us a test-tube full of the explosive.  He put it in my husband’s safe in the library.  Lord Wisbeach is convinced that these scoundrels are trying to steal this, but I cannot help feeling that this is another of those attempts to kidnap my son Ogden.  What do you think?”