"Why not?" I asked.

"Why not? It is as if you met a tram-car coming down a country
lane. Mycroft has his rails and he runs on them. His Pall Mall
lodgings, the Diogenes Club, Whitehall--that is his cycle. Once,
and only once, he has been here. What upheaval can possibly have
derailed him?"

"Does he not explain?"

Holmes handed me his brother's telegram.

Must see you over Cadogen West. Coming at once.

Mycroft.

"Cadogen West? I have heard the name."

"It recalls nothing to my mind. But that Mycroft should break
out in this erratic fashion! A planet might as well leave its
orbit. By the way, do you know what Mycroft is?"

I had some vague recollection of an explanation at the time of
the Adventure of the Greek Interpreter.

"You told me that he had some small office under the British
government."

Holmes chuckled.