The emotional roller coaster ride continues in the upcoming episode of "Elementary" season 6, and the drama will now be focused on Joan Watson (Lucy Liu) as a tragedy in her family will make her ponder on the past. The highlight of episode 2 will be the reunion of Joan with her half sister due to this tragedy. The viewers will also witness Sherlock Holmes (Jonny Lee Miller) handling a new case with Joan, although the awkwardness between the two will still be noticeable.

According to the latest synopsis for "Elementary" season 6 epsiode 2, titled "Once You've Ruled Out God," Joan will cross paths with her half sister, Lin Watson (guest star Samantha Quan), as they mourn over the death of their estranged biological father. Although, Joan has never been really close to her father, and neither has her sister. In spite of this, the two will have a lot to reflect upon following the death of their father. 

Joan and her half sister will have different ways of coping with their father's death, which is understandable as each of them had their own unique experience growing up. Joan may have a different reaction regarding her father's death compared to her sister, and this might also cause some issues between the two. Of course, the episode will not be over until they figure out a way to patch things up together.

On the other hand, Sherlock and Joan will be given another mission that involves hunting for a stolen plutonium package. The duo must be able to locate the material as soon as possible as the plutonium is suspected to be used to create a deadly bomb. This speculation is due to the death of an inspector from the department of energy, who was killed with the use of a lightning gun. The murder weapon could end up as a clue to pinpoint who is the mastermind behind the killing and the creation of a weapon for mass destruction.

It looks like Sherlock and Joan have a long way to go before they can start anew as partners. It can be recalled that the relationship of the two close comrades was shattered by the death of Shinwell (Nelsan Ellis). Joan was very close to Shinwell, although the latter tried to kill Sherlock that ultimately triggered a neurological problem with the popular crime detective. Sherlock, thinking that Joan will not be there by his side due to their recent conflict, will look for help from other people. 

"Elementary" season 6 episode 2 will air next Monday, May 7 at 10 p.m. EDT on CBS.