Sherlock Season 4: 18 Easter Eggs & References From 'The Lying Detective'

When acting delirious and dangerous at Baker Street, Sherlock energetically recites the famous "Once more unto the breach" speech from William Shakespeare's Henry V. Sherlock ends with the line "The game's afoot."

This line has, of course, been synonymous with the detective since Doyle used it in his stories. Modern Sherlock usually uses "The game is on", but previously said the original in The Abominable Bride.

In this same scene, Sherlock shoots the wall of his flat. He previously did this in The Great Game, where he shot into a yellow smiley face drawn on the wall. This was in turn a nod to when Holmes shot the initials V.R. (Victoria Regina) into the wall in The Adventure of the Musgrave Ritual.