Sherlock (Jonny Lee Miller) may be the best at solving crime mysteries, but he struggles at relationships, as seen in his partnership with Joan (Lucy Liu), which is about to take another turn for the worse.

Apparently, on the upcoming season 6, Joan will be losing a dear friend of hers who happens to be against her friendship with Sherlock. This may eventually convince her to cut ties with Sherlock for good. This friend's death may be a sign for Joan to reassess the choices she made and decide whether or not her partnership with Sherlock is actually a good thing. 

"Joan will lose someone who was very close to her once upon a time and she will learn that this person made certain assessments regarding the decisions Joan has made as a professional. It's going to give her cause to look at choices she's made and choices that she has right in front of her: Might she be a more complete person if she weren't in a partnership with Sherlock Holmes?" says executive producer Rob Doherty. 

As for which friend of Joan's, it is not yet known, but Doherty did indicate that he/she was not fond of Joan and Sherlock's friendship. 

Earlier in the previous seasons of the show, their relationship has already become strained. Sherlock's absence in Shinwell's (Nelsan Ellis) funeral was something Joan could not let go. In addition, Sherlock's reservations on telling Joan about his brain tumor have already caused tension between the two, though should he admit this in season 6, they might still have a chance.

Granted, if Sherlock does admit this to Joan, the latter may lessen her activity in the New York Police Department (NYPD) as a consultant in order to look after him. Otherwise, a new character may get introduced in the upcoming season and may shoulder the burden of taking care of the detective.

"Elementary" is a modern and American take on Sir Arthur Conan Doyle's classic character Sherlock Holmes. Its sixth season has no exact release date yet but is expected to arrive in 2018.