The episode 4 of "The Blacklist" Season 2 is titled "Dr. Linus Creel." The case of this episode is a social psychology experiment that yields deadly results. Normal, non-violent kind of people are transforming into deadly killers because of this experiment. Red tips off Liz about this dangerous experiment. The highlight of this episode, however, is likely to be the revelation about what Liz is hiding behind a closed exit door. Also, she will be meeting Red's former wife Naomi to find answers about her past.

"Her [Liz] life has been a mystery, but Liz's greatest secret lies just beyond the door," according to "The Blacklist" twitter account. Red has been hiding too many things from Liz while knowing almost everything about her past. In episode 2 of "The Blacklist" Season 2, it was hinted that Liz, too, is hiding something from Red. She did not tell Red the name of the source who provided her the much needed information on Berlin.

The buzz is that Tom is alive and he might be Liz's source. According to Entertainment Weekly (EW), Tom will make an appearance in flesh soon. In the last episode, he popped up in Liz's dream, telling her not to trust Red and that he will kill her once Berlin is no longer a threat to him. Also, he told her to ask Red about the fire.

EW says that Tom may find "some new allies" in a case of 'the enemy of my enemy is my friend'." It also adds that the current enemies Red and Berlin might actually team up in one of the upcoming episodes. When Berlin and Red met, Red told him that he did not kill his daughter and a common enemy must be benefitting from their battle.

Mr. Vargas is returning in episode 4. In the last episode, Naomi slapped Red. It is expected that these two are going to talk in "Dr. Linus Creel," revealing some details about Red's life as a government agent. Also, the preview suggests that the topic of Liz will come up. There are speculations that Red might kill Naomi.

Official synopsis of "The Blacklist" Season 2 Episode 4, "Dr. Linus Creel": "After a series of seemingly nonviolent citizens become killers, Red tips off Liz that a dangerous social-psychological experiment may be underway. Elsewhere, Red tries to convince Naomi and her husband into accepting a complicated proposition."

 [Youtube/The Blacklist]