Limitless episode 20 had FBI agent Rebecca Harris learn the truth about Brian's involvement with Senator Morra and who killed her father. Limitless was one of a number of movies to use the popular - but thoroughly debunked - theory that people only use 10% of their brain power, and they could unlock borderline supernatural abilities if they used 100%. Scarlett Johansson's action movie Lucy was another high-profile project that used this premise, while Limitless featured Bradley Cooper as a down on his luck writer who becomes rich and successful after taking a brain-altering pill dubbed NZT.
Unfortunately for Cooper's Eddie Morra, the pill has numerous side effects and it attracts a number of powerful enemies. The movie ended on an ambiguous note, with Eddie running for Senate and claiming to have weaned himself off the pill. Despite rumors of a sequel, Cooper's rising star following the success of the film led him to other projects like Silver Linings Playbook and American Sniper, meaning he was too busy for Limitless 2.
Instead of a movie sequel, Limitless was turned into a TV series instead, which is set four years after the film. The lead role is handed over to Brian Finch, played by Jake McDorman (Lady Bird), a singer who is recruited by Morra to act as a consultant to the FBI whilst feeding him information on their investigation into NZT. Cooper returned to play Morra on the show, though his role is mostly limited to brief appearances. Limitless was an entertaining procedural but it was cancelled by CBS after the first season due to an overall lukewarm reception.
One of the highlights of Limitless was the partnership between Brian and Rebecca Harris, the FBI agent he's paired with, played by Jennifer Carpenter (Dexter). Even without the use of the pill, Harris is a smart and dedicated agent who gradually comes to realize Brian's links to Morra as the show progress. Limitless episode 20 "Hi, My Name Is Rebecca Harris" finds her demanding Brian finally stop lying and come clean about everything.
Brian confesses his role as a spy for Morra and that series villain Sands, played by Colin Salmon (Krypton), is the one who killed her father. Harris' father was a drug addict and his death would play a big role in her decision to join the FBI, so she understandably takes this personally. She decides to take an NZT to give her brain the extra boost to track down Sands. She and Brian follow a trail to an ex-Morra employee, but as they follow up on the evidence they find, a sniper sent by Sands tries to kill them both. Harris uses her extra brain power to take him down with pinpoint accuracy.
When their clues lead to a dead end - literally, since the suspect they were chasing is found dead - they decide to communicate with Huston, a former associate of Sands. The only problem there is that he's in a coma, but since his brain is still active and this is Limitless, they fashion a design to communicate with him and he fills in the gaps. This leads to Sands being arrested and Rebecca achieving a little closure over her dad's death. She even has a brief vision of him saying goodbye.
Limitless episode 20 ends with Brian also deciding to step away from the FBI now the truth is out. It was a smart move making Rebecca the focus of the episode, and it proved the theory that if she took the NZT pill she'd be essentially unstoppable. That could have been a potential angle for Limitless season 2, but sadly, it didn't work out that way.