Sherlock Season 4: 20 Easter Eggs & References From The Six Thatchers

4. Work Is The Best Antidote To Sorrow

We also see Sherlock and Mrs Hudson grieving Mary back at Baker Street. When Sherlock says he will get himself a case, his landlady questions whether he is up to it. "Work is the best antidote to sorrow," Sherlock explains.

This is an apt quote lifted from The Empty House, the Doyle story in which Mary is first mentioned to have died (or, at least, is heavily hinted to). On that occasion, Sherlock says it to John:

"Work is the best antidote to sorrow, my dear Watson," said he.