In The Lying Detective Sherlock is still missing and John has figured out he’s alive.
John now has to get Mycroft to confess.
We know from The Sign of Three that Sherlock had Mycroft’s keys; from the web-episode Many Happy Returns that John has a recording of Sherlock’s voice; Lestrade’s I.D. card from A Study in Pink; Mycroft’s pass from Baskerville;he has been collecting passwords and usernames to disable the security in Mycroft’s house and access his computer (Eurus, Sherrinford, Redbeard, birthdate, Lady Bracknell, name of Sherlock’s friend).
“Impossible! You can’t have got out!”
After saying this, Mycroft can no longer ignore John’s questions.
This isn’t about Eurus, it’s John’s plan to bring Sherlock back.
