"Limitless" TV series star Jake McDorman, pictured here as Brian Finch in the hit CBS show, will have to choose between his life and his friends in episode 5. CBS

CBS' “Limitless” is starting to link back to the 2011 movie of the same name in very odd and troubling ways. As the mystery behind the super drug NZT grows thicker, the characters will have to figure out if solving the case is worth sacrificing their personal relationships in episode 5, titled "Personality Crisis."

After episode 4 saw Brian Finch (Jake McDorman) prove his loyalty to Senator Ed Morra’s (Bradley Cooper) people by stealing confidential FBI documents, it seems that they’re going to continue to put the pressure on him by asking him to do less than noble things. Among those unsavory tasks is removing Finch’s friend/FBI liason, Rebecca Harris (Jennier Carpenter) from the equation. Morra wants to make sure that her incessant digging into NZT doesn’t reveal his plan before it’s too late. Odds are good she’ll be looking into NZT more than ever now that Finch has discovered that her late father was linked to the drug as a distributor before he mysteriously died. It looks like episode 5 will see Brian wrestle with this new knowledge and whether or not to tell Harris, since he obtained the information through incredibly illegal means.

“Brian discovers a shocking secret about Rebecca’s late father, but worries that telling her will land him in legal trouble,” the episode’s plot synopsis reads (via TV Guide). “At the same time, he ends up meddling in her personal life while learning self-defense from her secret FBI boyfriend.”

It seems that Brian will be growing more attached to his FBI liason than he already has as this burning secret that he’s keeping draws him closer to Harris as a person and not as an agent. Still, with Morra breathing down his neck to show results and keep NZT out of the FBI’s crosshairs, he’ll have to choose whether his life and the life of his family is more important than Rebecca’s right to know the truth about her dad.

Luckily, despite poisoning his father and forcing him to commit treason, Morra isn’t such a bad guy after all. A clip posted to CBS’ official website teases Bradley Cooper’s return. The scene shows a rooftop confrontation in which Morra reveals that some of his more brutal tactics were just a test to see how far Brian would be willing to go. He explains to him that he’s not looking for a tool to inject NZT with, but rather a partner that can handle the drug and its side effects to become Morra’s partner. As to what end he needs Finch’s help, fans will just have to tune in to the rest of “Limitless” Season 1 to find out.

Episode 5, “Personality Crisis,” airs Tuesday at 10 p.m. EDT on CBS.