Repo Men

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In 2025, a corporation called "The Union" has perfected bio-mechanical organs to replace diseased organs. However, if they fall behind on payments, a "repo man" reclaims the artificial organ (artiforg) from the body; the procedure frequently results in the death of the customer due to them being crucial organs.
Remy and his partner Jake Freivald are considered the best of the Union's repo men. However, Remy's wife Carol disapproves of his work, believing that it is a bad influence for their son Peter. At a family barbecue, Jake does a quick repossession on a passenger in a cab using a kitchen knife. Carol sees this and leaves with Peter, urging Remy to make a decision. While out driving with Jake, they discover a "nest", a refuge for Union customers who have defaulted on payments for their artiforgs and become fugitives to avoid the repo men. Remy and Jake raid the nest by themselves and reclaim 32 artiforgs, which impresses their boss Frank. He offers them the opportunity to become full-time raid captains. Remy refuses and attempts to ask Frank to transfer to sales, but Jake cuts him off. Jake tells Remy that what they do is important, but Remy's mind is made up. Jake suggests that Remy's last job be a musician that Remy is a fan of. After helping the musician finish one last song, he uses a defibrillator in order to stop the artificial heart, but the device malfunctions, and Remy is severely injured, requiring replacement of his heart with an artiforg.
Carol divorces Remy for taking another job, so he moves in with Jake. In sales, he is unable to lie to potential customers about the consequences of non-payment and is forced back into repo to pay for his heart, but has developed sympathy for his victims and develops a psychological block that prevents him from repossessing their artiforgs. He soon goes into severe debt, even resorting to gambling to try and earn money. Jake discovers that Remy has not been repossessing and takes him to a "nest" with enough artiforgs to clear his debt; however, Remy cannot do the job. Furious, Jake demands he stay there until he gets over his inhibition. A stunned debtor wakes up and knocks Remy out.
Waking up, Remy encounters Beth, a singer he would see while drinking in a bar with Jake. He takes her to a motel room and discovers she has numerous artiforgs. Remy attempts to clear Beth's and his own accounts, but he is interrupted by Jake, who lets him leave. On the run, Beth and Remy leave for the abandoned outskirts of the city. Beth tells Remy of how she contracted various diseases and was involved in a car crash, and was forced to resort to buying artiforgs on the black market after running up severe debts. They begin a relationship, and Remy decides to document his life as a repo man with an old typewriter Beth found. As he works on a manuscript, he is interrupted by a repo man. Remy sets a trap and the collector drops through a hole in the floor. Beth falls through the same hole, damaging her prosthetic knee. Before the collector can shoot Beth, Remy manages to kill him.
Remy sneaks into his former workplace to obtain scanning jammers he had confiscated during his raid on the nest. He attempts to force Frank to clear his account, only to discover that accounts can now only be cleared at the Union's central office due to his earlier attempt. Remy and Beth attempt to flee the country at the airport, but security is alerted by bleeding from Beth's knee. A fight with airport security ensues. Jake finds them, but is on the wrong side of a security panel and watches their escape. They go to a black market doctor to replace Beth's knee.
After the procedure, they are stopped by Jake who tries to convince to Remy to rejoin him as a repo man. Remy refuses, and Jake reveals he rigged the defibrillator unit so Remy would continue to work with him. They fight, and Jake knocks Remy unconscious. Beth awakens Remy, saying she stunned Jake as an organ repossession raid is underway. They flee and Remy decides to delete the accounts of all implant clients. Remy meets Carol and Peter on a train one last time, passing on his manuscript to Peter.
Remy and Beth break into Union headquarters and fight their way through the facility to the Union's database. Using Beth's prosthetic eye, they enter and seal themselves inside as Jake and Frank arrive. The server's only interface is an organ scanner, requiring Remy and Beth to cut themselves open to use the scanner internally, clearing their accounts. Frank and Jake enter the server room using an artiforg from one of the slain repo men, just as Beth has flatlined. Remy tries to scan the last organ and revive her as Frank orders Jake to kill him. Jake asks Remy if Beth is worth it, and he responds, "She's worth every job we ever did." Frank attempts to kill Remy himself, but Jake stabs him in the throat before helping to revive Beth. Jake tosses two grenades into the artiforg drawer of the server, with the explosion destroying the mainframe, wiping the records of everyone who has an account with the Union.
Later, Remy is seen on a tropical beach, enjoying his freedom with Beth and Jake. His text has been published as a book, The Repossession Mambo. While Remy talks to Jake, he notices that Jake suddenly disappears, leaving Remy's book on his chair; then Remy sees the beach flicker with static before returning to normal. It is revealed that Remy is in a coma, having sustained severe brain damage when Jake hit him. Jake has paid off Remy's debt for his heart and also paid to link his brain to a neural network, allowing him to live out his life peacefully in a computer generated dream world. Beth is unconscious, and Jake says he will take care of her; he then says a sorrowful goodbye to Remy. The film ends with Frank delivering a sales pitch for the neural network.

Question: Where does Beth go to get her knee replaced?
Answer: She goes to a black market doctor.