“A singular set of people, Watson - the man himself the most singular of them all. I managed to see him on a plausible pretext, but I seemed to read in his dark, deep-set, brooding eyes that he was perfectly aware of my true business. He is a man of fifty, strong, active, with iron-gray hair, great bunched black eyebrows, the step of a deer, and the air of an emperor - a fierce, masterful man, with a red-hot spirit behind his parchment face. He is either a foreigner or has lived long in the tropics, for he is yellow and sapless, but tough as whipcord. His friend and secretary, Mr. Lucas, is undoubtedly a foreigner, chocolate brown, wily, suave, and catlike, with a poisonous gentleness of speech. You see, Watson, we have come already upon two sets of foreigners - one at Wisteria Lodge and one at High Gable - so our gaps are beginning to close.

“These two men, close and confidential friends, are the centre of the household; but there is one other person who for our immediate purpose may be even more important. Henderson has two children-girls of eleven and thirteen. Their governess is a Miss Burnet, an Englishwoman of forty or thereabouts. There is also one confidential manservant. This little group forms the real family, for they travel about together, and Henderson is a great traveller, always on the move. It is only within the last few weeks that he has returned, after a year’s absence, to High Gable. I may add that he is enormously rich, and whatever his whims may be he can very easily satisfy them. For the rest, his house is full of butlers, footmen, maidservants, and the usual overfed, underworked staff of a large English country-house.

“So much I learned partly from village gossip and partly from my own observation. There are no better instruments than discharged servants with a grievance, and I was lucky enough to find one. I call it luck, but it would not have come my way had I not been looking out for it. As Baynes remarks, we all have our systems. It was my system which enabled me to find John Warner, late gardener of High Gable, sacked in a moment of temper by his imperious employer. He in turn had friends among the indoor servants who unite in their fear and dislike of their master. So I had my key to the secrets of the establishment.

“Curious people, Watson! I don’t pretend to understand it all yet, but very curious people anyway. It’s a double-winged house, and the servants live on one side, the family on the other. There’s no link between the two save for Henderson’s own servant, who serves the family’s meals. Everything is carried to a certain door, which forms the one connection. Governess and children hardly go out at all, except into the garden. Henderson never by any chance walks alone. His dark secretary is like his shadow. The gossip among the servants is that their master is terribly afraid of something. ‘Sold his soul to the devil in exchange for money,’ says Warner, ‘and expects his creditor to come up and claim his own.’ Where they came from, or who they are, nobody has an idea. They are very violent. Twice Henderson has lashed at folk with his dog-whip, and only his long purse and heavy compensation have kept him out of the courts.

“Well, now, Watson, let us judge the situation by this new information. We may take it that the letter came out of this strange household and was an invitation to Garcia to carry out some attempt which had already been planned. Who wrote the note? It was someone within the citadel, and it was a woman. Who then but Miss Burnet, the governess? All our reasoning seems to point that way. At any rate, we may take it as a hypothesis and see what consequences it would entail. I may add that Miss Burnet’s age and character make it certain that my first idea that there might be a love interest in our story is out of the question.