Was it not more natural to suppose that this event proved that the detective was unknown to the thief?
Such being the case, Colonel Richmond, his nephew and Mrs. Pond were acquitted at the start.
It may seem ridiculous to suspect them, in any case, but so strange was the nature of this affair that Nick gave nobody the credit of certain innocence.
Colonel Richmond was certainly very nearly crazy on one point. He might be so much of a lunatic as to commit these robberies from simple delusion. Or he might wish to prove to his daughter that the diamonds were not rightfully hers.
Mrs. Pond might be pawning them for small extravagances which she was afraid to have known.
As to Horace Richmond, there was no motive which seemed plausible. The value of the articles taken was so small as to make the game not worth while for a man in his position.
And it was perfectly certain that no professional thief or dishonest servant was doing the work.
If such a person had been in the game, he would not have taken one of those diamond pins; he would have taken all three.
It was impossible to lose sight of the fact that the Stevenses would be the real gainers, if this ghost business led Colonel Richmond to insist that his daughter should give up the jewels.
Mrs. Stevens and her daughter could not be doing the job personally, but they might have a secret agent among the servants, or more probably concealed in some secret recess of the strange old house.