“That should be helpful, Watson,” he remarked as we took our seats in the Woolwich train. “We certainly owe Brother Mycroft a debt for having introduced us to what promises to be a really very remarkable case.”

His eager face still wore that expression of intense and high-strung energy, which showed me that some novel and suggestive circumstance had opened up a stimulating line of thought. See the foxhound with hanging ears and drooping tail as it lolls about the kennels, and compare it with the same hound as, with gleaming eyes and straining muscles, it runs upon a breast-high scent⁠—such was the change in Holmes since the morning. He was a different man from the limp and lounging figure in the mouse-coloured dressing-gown who had prowled so restlessly only a few hours before round the fog-girt room.

“There is material here. There is scope,” said he. “I am dull indeed not to have understood its possibilities.”

“Even now they are dark to me.”