In a two-part episodic event, Holmes’ (Jonny Lee Miller) former protégé Kitty Winter (Ophelia Lovibond) returns to New York after a three-year absence to warn Sherlock that a killer, whom they tracked in London, is eliminating anyone who was involved in the case. As we previously teased , Kitty also returns with a major bombshell secret relating to a new man in her life.

“When we last saw Kitty, she was on the run,” executive producer Jason Tracey says. “There was blood on her hands. She didn’t know if she’d ever see Sherlock and Joan again. In the years since, she’s done a lot of healing, and a lot of growing up – but she’s still as complicated as ever. Kitty is the only person who has ever become part of Sherlock and Joan’s family. Bringing her back, we get to find out if she still fits and if there’s room for their family to grow again.”