Episode 21 of "Elementary" season 5 is going to continue with the story of Marcus (Jon Michael Hill) and his girlfriend Chantal (Chasten Harmon).

In the previous episode of the American crime drama series, Chantal remained unconscious after being assaulted by a still unknown person. Her ex-husband Roy (Robert Christopher Riley) was the primary suspect, as it was not the first time he got involved in the lives of Chantal and Marcus.

The official synopsis for the upcoming episode titled "Fly into a Rage, Make a Bad Landing" reveals that Chantal will continue to be unconscious, with Roy still the main suspect of the crime. However, the situation will become more complicated when Roy is killed shortly after.

As Sherlock (Jonny Lee Miller) and Joan (Lucy Liu) look into the case, they discover that it is a staged suicide. With this, they look for another suspect who is linked with the crime. Nonetheless, as Sherlock looks at the clues, he discovers a heartbreaking realization about Marcus' past that may have something to do with the crime.

On the other hand, Marcus will look for other means of justice. In the spoiler room on TVLine, executive producer Rob Doherty said, "Of course, all eyes are on her ex-husband Roy. And Marcus is understandably upset and angry and wants to be part of the investigation."

However, since he is also hugely involved in and affected by the situation, Marcus has the tendency to make some mistakes and perhaps hasty decisions. Doherty continues, "An emotional cop tends to make mistakes."

The executive producer also hinted what the Sherlock will do to deal with this. He said, "While the police are conducting the official investigation, Sherlock enlists Marcus into a separate and perhaps more compelling investigation into Roy."

"Elementary" season 5 episode 21 airs on Sunday, April 30, at 10 p.m. EDT on CBS.