Sherlock (Jonny Lee Miller) and Joan (Lucy Liu) are going to look for two murderers in next Sunday’s episode of “Elementary.”

In the preview clip for Season 5, episode 7, titled “Bang Bang Shoot Chute,” the crime-solving duo investigates the death of a base jumper who is killed in mid-air. Although it is confirmed early in the investigation that the base jumper is shot before landing to the ground, Joan is convinced that the skydiver is murdered by two different people. “He wasn’t just shot. His parachute was sabotaged,” the former surgeon says of the victim in the video.

According to the preview clip, there are at least four suspects for the murder of the base jumper: his wife, his sister, his skydiving partner and the pilot of the plane.

Meanwhile, the episode also marks the return of Joan’s real estate agent sister, Lin (Samantha Quan). According to the synopsis for the episode, Lin thinks she sees Shinwell (Nelsan Ellis) with a member of his old gang. After learning this from her sister, Joan takes drastic measures to make sure that the ex-con won’t be drawn back into his old life.

Quan’s return to the show was first revealed last month. While live-tweeting Season 5, episode 2, titled “Worth Several Cities,” co-executive producer and writer Robert Hewitt Wolfe wrote on Twitter that the 41-year-old actress is set to reprise her role in the current season’s episode 7.

Lin made her series debut in Season 4, episodes 19 and 20, which were aired back-to-back last April. In the episodes, Joan learned for the first time that Lin is actually her half-sister. Lin was last mentioned by Joan in Season 5, episode 2 when she told Shinwell that she got his new apartment with the help of her sister.

“Elementary” Season 5, episode 7 airs on Sunday, Nov. 20 at 10:30 p.m. EST on CBS.