(Facebook/NBCBlacklist)Promotional image for the return of "The Blacklist" season 4

Theories about the secret that Red (James Spader) revealed to Alexander Kirk (Ulrich Thomsen) emerge as fans continue to wait for the return of "The Blacklist" season 4.

Toward the end of the midseason finale titled "Dr. Adrian Shaw: Conclusion," Kirk was about to inject poison on Red's neck to kill him. But Kirk stopped in his tracks when Red whispered something to him at the last minute.

While some fans believed that Red might have admitted that he and Kirk are somehow related, others offered a more outrageous theory regarding Red's secret.

According to some speculations, Red might have told Kirk that Liz (Megan Boone) is really his daughter. But he constantly told Liz in the past that he is not his father. This is why fans believed that Red is actually Liz's mother Katarina Rostova (Lotte Verbeek).

The speculations pointed out that Katarina's body was never found after she allegedly committed suicide. Also, the fact that Red is being constantly visited by Katarina on his mind might be a sign that the old version of Liz's mother is talking to her new version.

But executive producer Jon Bokenkamp found such theories absurd. In an interview with Entertainment Weekly, the executive producer said that the so-called "Mommy Theory" is funny. "I've heard that theory before and it's a wild one. I'd love to have someone walk me through the logic of exactly how that would work," Bokenkamp stated. "I've also heard that Liz is Tom's sister, Liz is a robot, and Ressler is Tom's brother. All great theories, by the way," he added.

While Red's secret remains a mystery, he will continue working with the Federal Bureau of Investigation (FBI) in the next episode of "The Blacklist" titled "Lipet's Seafood Company."

According to the synopsis for the episode that was posted on The Futon Critic, the FBI will investigate the operation of an international terrorist cell in the United States. But Aram (Amir Arison) will have to face the consequences of the hacking committed by his girlfriend on the FBI's computer systems. This will give Red an opportunity to reap a reward for doing a favor.

NBC will air the return of "The Blacklist" on Thursday, Jan. 5, 2017.