'The Blacklist' Creator Breaks Down Game-Changing Final Scene Shocker (Exclusive)

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Creator Jon Bokenkamp talks to ET about the surprising final scene from Wednesday's episode.

Warning: Spoiler alert! Do not proceed if you have not watched Wednesday's episode of The Blacklist.

Well, this will certainly change things.

In the final moments of Wednesday's episode of The Blacklist, Elizabeth Keen (Megan Boone) learned a long-lost family secret that will throw a major wrench in her plans: She has a sister. Jaw, meet floor.

The revelation comes unexpectedly for Liz, who tracks Ian Garvey's whereabouts to an out-of-the-way Parisian restaurant, which leads her to a young female employee with whom he has a friendly rapport. Looking for answers, she approaches the young woman named Lilly (Fiona Dourif) in an attempt to get her to help take down Garvey, the man responsible for Tom's murder. After Liz shows Lilly every clue she's rustled up against Garvey so far, Liz discovers there's more to Lilly than meets the eye. Turns out, she's been in Witness Protection for most of her life and is, wait for it, also Raymond Reddington's (James Spader) daughter. Her real name? Jennifer.

"This reveal that Lilly is Liz's sister has been something we've been sitting on for a long time," creator Jon Bokenkamp tells ET. "This is somebody who can upend things potentially in a very dangerous way for Reddington." In the second season, fans may remember meeting Naomi Hyland (Mary-Louise Parker), Red's ex-wife from his pre-crime days, where it was established that the couple had a daughter named Jennifer. After Reddington fled, Naomi and Jennifer were forced to relocate and give up everything they'd ever known. Up until this point, it was unclear what had happened to Jennifer. Now, we have the answers.

"They were estranged. He was searching for her. He wanted to reach out to her and make contact, and this woman, Jennifer, wanted nothing to do with Reddington. She's been living in hiding and trying to have a life outside of his shadow, which is very difficult to do," Bokenkamp says. "We knew that this season would ultimately point us to a very emotional and character-driven place because it continues to be even more of a family drama in a strange way."

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But why spring this family revelation on Liz now? As Bokenkamp tells it, Liz -- who's been on a race against Reddington to get to Garvey first -- has completely shed her old skin, adopting a ruthless outlook when it comes to avenging her husband's gruesome death. What better way to derail Liz's plan than to introduce a long-lost sister into the picture?

"This is a very different Elizabeth Keen than we met in the pilot and at the beginning of season five. She is not only trying to solve the mystery the audience is trying to solve, of what is in this duffle bag, she's trying to avenge the death of her husband. She's essentially given her daughter up for adoption and she's been stripped down to a very raw, emotional and pretty angry place," Bokenkamp explains. "To introduce her to this estranged sister and to see what she does with that information is going to be really compelling in the coming episodes."

So how exactly does Liz go about navigating this new piece of information? "Liz might view her sister as more of a witness or a bargaining chip or a partner in crime than a long-lost sister. We're not really interested in doing the soap opera in doing the [story of] two sisters reunited. Liz is going to embrace this relationship, but not because she's trying to get close to somebody she loves because of the familial relationship. She views it as potential ammunition against Reddington in what is continuing to be a bigger and bigger divide between the two characters."

With Liz and Reddington on a collision course to get to Garvey (each for very different reasons: Liz wants to expose the truth in the bag of bones, while Reddington wants to shield it), "the larger question of who these bones belong to and what they mean is something that is going to fuel a good conflict between the two leads," Bokenkamp hints. 

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The conversation between Liz and her sister also brings to light differing viewpoints on the awfulness of Garvey and Reddington. While Liz has harbored a disdain and hatred for Garvey, most of it due to the fact that he killed Tom, Lilly/Jennifer has a much more empathetic opinion.

"Jennifer opens a window to a larger version of the truth. She has a different perspective on who Ian Garvey is. She has a much deeper understanding of this man and has answers, potentially, that Liz knows nothing about," Bokenkamp says. "To all of a sudden meet somebody from 30 years ago who has a history with Reddington, forgetting that she's her sister, this is somebody who has, potentially, information. The idea that it might shift our perspective on who Garvey is, is an interesting one. That's what Liz is leading with. She's filled with questions for this young woman."

Bokenkamp also addressed Liz's candidness in bringing in a relative stranger into her home and filling her in on the long-game mystery, saying it "speaks to how she's operating outside the rules."

"One of the interesting questions that comes up in the next episode is what does she do with the revelation that she has found her estranged sister. Does she tell Reddington? Does she go to the FBI? She didn't go straight to the police and say, 'Hey, I have new information,' she took her to her apartment and revealed to her in a very candid way the mystery she's been working on," Bokenkamp points out. "Liz, who we've seen stew someone this season in a bathtub with chemicals, now has a very credible witness under her wing. Seeing the choices she makes might be surprising."

Now that Liz is a step ahead of Reddington in their race, the re-emergence of Jennifer into the picture will "bring up questions of [Liz's] own morality," Bokenkamp says, "of what she's willing to do, of what line she's willing to cross and uncover this larger truth that Reddington is determined to keep a secret."

The Blacklist returns Wednesday, April 25 at 8 p.m. ET/PT on NBC.

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