"The Blacklist" is airing its Season 4 winter finale this week. Viewers will see a different side of Red (James Spader) in the episode.

Episode 15 titled "The Apothecary" will showcase Red being dosed with a fatal poison. He will try to retrace his steps to find out who among his closest confidants betrayed him and put him in harm's way, SpoilerTV reported.

Liz (Megan Boone) and the Task Force are equally desperate to find answers. They will have to hurry, though, given that Red only has a limited time before the poison spreads throughout his body.

This predicament might sever Red's ties with the FBI, especially Cooper (Harry Lennix). The latter's patience with the former criminal mastermind is wearing thin and he might consider rescinding his deal with Red.

This comes in a really bad timing for Red, who desperately needs the FBI's assistance now more than ever. The task force's help would be greatly appreciated in searching for the person who poisoned Red. Viewers speculate that either Mr. Kaplan (Susan Blommaert) or Dembe (Hisham Tawfiq) is the culprit.

"The Blacklist" producers confirmed that there will be a major cliffhanger in the finale. Lennix teased that he didn't see the whole thing coming and praised the show's writers for having "a unique gift at being able to open up and dig down new rabbit holes." He added that "The Apothecary" will answer plenty of viewers' questions and "raise new possibilities" at the same time, according to TVGuide.

One of the series' main characters, Tom Keen (Ryan Eggold), is exiting the show for its spinoff, "The Blacklist: Redemption." The series landed Enrique Murciano in a key role to fill the position that Eggold vacated.

Murciano will portray Julian Gale in the last four episodes of Season 4, with a series regular option in Season 5 if the show gets renewed by NBC, Deadline reported. Gale is an FBI investigator and former associate of Ressler (Diego Klattenhoff).

Gale was described as a man whose "obsessive tendencies make him both a valuable agent and a potential liability." He's committed, driven, commanding and charismatic, though he has a tendency to lose himself in his new assignment.

"The Apothecary" airs on Thursday, Feb. 23 at 09:00PM - 10:00 p.m. on NBC. Who do you think poisoned Red? Share your thoughts below! "The Blacklist" Season 4 will resume in April.