Holmes' former protégé, Kitty Winter, warns him of a killer who is eliminating everyone involved with a case they worked on together in London; Watson discovers that Kitty has a lifechanging secret.
Joan and Kitty try to prove that a string of murders is connected to an international government conspiracy involving the Defense Intelligence Agency; Sherlock and Kitty's relationship is strained after she shares lifechanging news.
Following a mysterious and catastrophic incident in the precinct, Bright faces an internal affairs review as Gil and the team worry about his mental health.
