Blake Lively is out for revenge in The Rhythm Section, and here's what happens at the end of the spy-thriller. Based on the successful book series by Mark Burnell, The Rhythm Section is now out in theaters following multiple delays. Directed by Reed Morano, The Rhythm Section stars Lively as Stephanie Patrick, who begins a quest for revenge after learning that the people responsible for the bombing of Flight 147 - which killed her father, mother, brother, and sister - are still alive.

Life hasn't been easy for Stephanie since the loss of her family, with The Rhythm Section introducing her to audiences when she's a prostitute and drug addict. She learns that there is more to their deaths thanks to journalist Keith Proctor (Raza Jaffrey). He shares information he's gathered about the bombing with her. He believes that the attack was a cover-up assassination attempt on Islamic reformer Abdul Kaif. Proctor has also learned that the bomber, Reza Mohammed (Tawfeek Barhom), is alive and even in London. Stephanie decides she must strike now to get revenge, but she can't go through with shooting Reza, and that decision proves costly. Reza steals her bag filled with Proctor's information and kills him at his apartment.

Related: The Rhythm Section Cast & Character Guide

Alone again, Stephanie is left with one option: find Proctor's source "B" (Jude Law) in Scotland. Once they are acquainted, "B" decides to train her so she has a chance to get her revenge without dying. After months of training, Stephanie takes on a new life as Petra Reuter - a former assassin that "B" killed - and is sent out on her first mission. She must work with information broker Marc Sarra (Sterling K. Brown) and uses the information given to her to kill those who are tied to the bombing and the operation's mastermind U-17. These missions build to a finale that offers Stephanie the shot at revenge she seeks.

What Happens In The Rhythm Section's Ending

Blake Lively in The Rhythm Section Movie

The Rhythm Section ending is put into motion following Stephanie's failed assassination attempt on the wealthy businessman Leon Giler (Max Casella), who has ties to the plane bombing. She doesn't kill him after learning he has kids, but "B" had a contingency plan in place to make sure the job got done. Unknowingly, this results in the deaths of Giler's children too. This prompts Stephanie to leave "B" behind and work directly with Sarra to find Reza. She learns that U-17 hired Sarra to find someone to eliminate Giler, as U-17 is believed to be getting rid of anyone with knowledge of what happened before. This leads Sarra to suggest that Reza is U-17.

Stephanie goes to Marseille to kill Reza and sees that he's preparing for another bombing. After a brief shootout, Stephanie follows Reza and a girl with a bomb vest onto a bus. She attacks Reza and buys enough time for the bus to be cleared out, as the bomb is on a timer. As Stephanie is about to kill Reza, he warns her that Sarra is going to kill her next. She escapes from the bus before the bomb explodes and goes back to Sarra's house. Stephanie tells Sarra about her past and that she isn't Petra as she injects him with a lethal venom she acquired on a previous mission. She figured out that Sarra was actually U-17.

After her successful revenge trip, Stephanie returns to the Kaif household, as the parents of Abdul provided the necessary funding for her missions. Two weeks later, "B" surprises Stephanie with a visit and tells her that its time for Petra to be dead again. Stephanie agrees as she is no longer using that alias anyway. The Rhythm Section ends as Stephanie walks away from "B" for what he hopes is the last time he'll ever see her.

Rhythm Section Villain: U-17 Explained

Sterling K Brown and Blake Lively in The Rhythm Section

The identity of U-17 is undoubtedly the biggest mystery at the center of The Rhythm Section, and some may be surprised to learn that it is Sarra. U-17 is essentially the mastermind behind the bombing attack, but Sarra being the previously unidentified person shows just how plugged in he was. The movie reveals that the CIA was on his trail before the bombing of Flight 147. The original Petra was hired by the organization to kill him, but "B"'s desires got in the way of her completing this mission. It isn't specified if Petra was hired to kill Sarra because the CIA suspected the bombing of Flight 147 or if it was for another reason. After all the secrecy, though, it was Sarra's suggestion to Stephanie that someone as inconsequential as Reza could be U-17 that tipped her off to his real identity.

Every Person Connected To The Bombing Stephanie Kills

Blake Lively in The Rhythm Section

Throughout The Rhythm Section, Stephanie's hope for revenge takes her on several different deadly missions. The first takes her to Tangier to kill Lehmans, the man who arranged for the bomb to be on Flight 147. Stephanie has to pay Sarra 200,000 euros for this information, and Lehmans dies after not being able to use his oxygen machine. Stephanie's next mission is to New York and to kill Leon Giler. Although she does not go through with the assassination, her involvement still leads to his death. She then goes to meet Reza and makes sure he dies from the bomb he designed, and she then ends Sarra/U-17's life to close out her current revenge needs.

Why Stephanie Wasn't On The Plane With Her Family

Blake Lively in The Rhythm Section

One question that audiences are sure to have early on during The Rhythm Section is why Stephanie wasn't on the plane with the rest of her family. The movie plays a voicemail Stephanie has from her mom that asks her to bring her father's wedding ring to the airport, as he forgot it at home, indicating that Stephanie was supposed to be on Flight 147 as well. We later learn that this flight was specifically chosen to ensure that Stephanie could go on the trip with her family, but she reveals that she simply decided she didn't want to on that day. So, not only does she want revenge on those who killed her family, but she also has an incredible amount of guilt for making them take that flight and then not going. It's a catalyst that influences the rest of her choices.

Rhythm Section Movie's Biggest Book Differences

Blake Lively in The Rhythm Section

Since The Rhythm Section is based on a book, there may be some viewers who go into the movie familiar with Stephanie and her story - but this film has significant differences to the novel. One change that is apparent early on is how quickly the movie gets Stephanie involved with Proctor. In the book, readers get to spend more time with Stephanie coping with the death of her family members, but the movie has Stephanie meet Proctor almost immediately. And speaking of Stephanie's family, the book and film are different in that regard too, as all of her family members die on the plane in the movie, but she has one brother who is still alive in the book.

The Rhythm Section movie also consolidated a major part of the book into a composite character that became "B." In the book, Stephanie's first attempt to kill Reza is stopped by an antiterrorist organization known as Magenta House. They kidnap her and offer to train her to be one of their agents so she can adequately kill Reza. This organization is lead by a man named Alexander, but Magenta House is nowhere to be seen in The Rhythm Section. Instead, "B" is the one who trains Stephanie, but only after she finds him. Stephanie also falls in love with her neighbor Frank in the book. She settles down with him at the end, leading to Alexander stopping by and Stephanie threatening his life if he came back again, but the only romance Stephanie has in the film is when she hooks up with Sarra.

Another change to the book is the location of the final confrontation with Reza and the context of it. The book has no mention of U-17, which keeps Reza as the primary target for Stephanie. The two meet again as Reza is trying to hijack another plane and not trying to bomb a protest, as is the case in the film. The Rhythm Section book also provides insight into what Reza's motivations are for this second bombing, as he's also trying to get revenge on those who killed his family members.

How The Rhythm Section's Ending Sets Up A Sequel

Blake Lively in The Rhythm Section

With this story and end, The Rhythm Section ending doesn't directly set up a sequel for Blake Lively to star in, but it also doesn't close the door on one happening. The final exchange between Stephanie and "B" works as a conclusion of this film. However, his hope to never see her again would also work as a subtle way to have him reluctantly reach out to her in the future. After all, everyone connected to the plane bombing is dead, so Stephanie no longer needs revenge.

If The Rhythm Section does get a sequel (which isn't a sure thing after the reviews), then the three sequel novels written by Burnell could serve as inspiration for future stories. Adapting them will require some changes based on the differences that already exist unless an organization like Magenta House is introduced in the sequel to draw Stephanie back into this lifestyle. Either way, The Rhythm Section ending leaves Stephanie in a place where her story can go in almost any direction.

Next: What To Expect From The Rhythm Section 2