Chapter 27: Corvath Surfaces — The Meeting at Blackfriars Bridge

The note was already on the kitchen table when Watson stood up.

He had not seen anyone deliver it. Lestrade had not seen anyone deliver it. They stood looking at it for a moment in the way that men look at a thing when accepting what it means is more difficult than understanding it. The envelope was cream-coloured, good stock, addressed in a hand Watson had never seen before but recognised instantly, in the way one recognises a voice heard only through walls: precisely formed, unhurried, with the particular economy of someone for whom unnecessary motion was a kind of error.

It contained a single card. No salutation.