When CBS' "Elementary" returns with episode 21 of season 5, the detective duo Sherlock Holmes (Jonny Lee Miller) and Joan Watson (Lucy Liu) will be investigating the murder of a reality show contestant.

As revealed in the synopsis of "Elementary" season 5 episode 21, titled "Moving Targets," the detectives will be looking into the murder victim's fellow competitors. "We're looking for a sore loser on a game show," Sherlock can be heard saying in the trailer for the episode. The contest's prize serves as motive for the murder. Detective Marcus Bell (Jon Michael Hill) says in the trailer, "Million dollars is pretty strong motive for murder."

Even though the pool of suspects has been limited, catching the perpetrator may serve as a challenge for the detectives as the killer is perhaps the most skilled murderer they have ever encountered, the synopsis reveals.

"In all our years together, we've never seen a more accomplished killer," Sherlock told Joan in the trailer.

Elsewhere in the episode, viewers will see the ex-con Shinwell Johnson (Nelsan Ellis) ask another favor from Joan. This, however, will be the first time he will reach out to her since he attacked Sherlock.

Shinwell will pursue his goal of infiltrating the ranks of the SBK gang. To move higher up the ladder, he needs to get rid of a member. Thus, he urges Joan to help him send the gang member behind bars. Shinwell believes that doing so will get him up the ranks.

Liu directed "Moving Targets," making it the fourth "Elementary" episode she has directed. Prior to this, Liu directed episode 22 of season 2, titled "Paint it Black;" episode 14 of season 3, called "The Female of the Species," and episode 22 of season 4, titled "Turn it Upside Down."

"Elementary" season 5 episode 21, "Moving Targets," will air this Sunday, May 7, at 10 p.m. EDT on CBS.