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

Casual viewers might be confused by the man making Sherlock "cups of tea" or "coffee" in his kitchen/meth lab.

This is Billy Wiggins, played by Tom Brooke. Appearing in His Last Vow, he was Sherlock's drug dealer who showed promise in the area of deductive reasoning. He liked to think of himself as Sherlock's "protégé."

Wiggins is a loose adaptation of two figures from the canon. Billy was the page-boy who helped Mrs Hudson out at Baker Street and Wiggins was the leader of the Baker Street Irregulars, Holmes' network of homeless urchins who would provide him with information.