Most of that morning we spent with them on the hillside.  Charles took them everywhere and showed them everything.  He pretended to be polite to the scientific man, and he was really polite, most polite, to the poetical lady.  Before lunch time we had become quite friends.

The Clays were always easy people to get on with; and, bar their roguery, we could not deny they were delightful companions.  Charles asked them in to lunch.  They accepted willingly.  He introduced them to Amelia with sundry raisings of his eyebrows and contortions of his mouth.  “Professor and Mrs. Forbes-Gaskell,” he said, half-dislocating his jaw with his violent efforts.  “They’re stopping at the inn, dear.  I’ve been showing them over the place, and they’re good enough to say they’ll drop in and take a share in our cold roast mutton;” which was a frequent form of Charles’s pleasantry.

Amelia sent them upstairs to wash their hands—­which, in the Professor’s case, was certainly desirable, for his fingers were grimed with earth and dust from the rocks he had been investigating.  As soon as we were left alone Charles drew me into the library.

“Seymour,” he said, “more than ever there is a need for us strictly to avoid preconceptions.  We must not make up our minds that this man is Colonel Clay—­nor, again, that he isn’t.  We must remember that we have been mistaken in both ways in the past, and must avoid our old errors.  I shall hold myself in readiness for either event—­and a policeman in readiness to arrest them, if necessary!”

“A capital plan,” I murmured.  “Still, if I may venture a suggestion, in what way are these two people endeavouring to entrap us?  They have no scheme on hand—­no schloss, no amalgamation.”

“Seymour,” my brother-in-law answered in his board-room style, “you are a great deal too previous, as Medhurst used to say—­I mean, Colonel Clay in his character as Medhurst.  In the first place, these are early days; our friends have not yet developed their intentions.  We may find before long they have a property to sell, or a company to promote, or a concession to exploit in South Africa or elsewhere.  Then again, in the second place, we don’t always spot the exact nature of their plan until it has burst in our hands, so to speak, and revealed its true character.  What could have seemed more transparent than Medhurst, the detective, till he ran away with our notes in the very moment of triumph?  What more innocent than White Heather and the little curate, till they landed us with a couple of Amelia’s own gems as a splendid bargain?  I will not take it for granted any man is not Colonel Clay, merely because I don’t happen to spot the particular scheme he is trying to work against me.  The rogue has so many schemes, and some of them so well concealed, that up to the moment of the actual explosion you fail to detect the presence of moral dynamite.  Therefore, I shall proceed as if there were dynamite