The entire narrative of "The Prestige" is a grand magic trick played on the audience, with two major reveals in its final act. The first and most central twist is the secret to Alfred Borden's "Transported Man": Alfred Borden is not one person, but two identical twin brothers. They have been living a single, shared life to protect their secret. One twin loves Sarah, while the other loves their assistant, Olivia. This explains Borden's seemingly erratic behavior, Sarah's accusations that some days he doesn't love her, and how he can be in two places at once. The twin who loved Sarah is the one who is ultimately hanged for Angier's apparent murder, while the other twin, who acted as the disguised engineer 'Fallon', survives to kill Angier and reunite with his daughter.
The second twist reveals the horrifying method behind Robert Angier's "Real Transported Man." Angier did not have a twin, so he used a machine built by Nikola Tesla that creates a perfect, living duplicate of an object or person. Each night of his performance, Angier would step into the machine, which would create a clone of him elsewhere in the theater (the 'prestige'). Simultaneously, a trapdoor would open beneath the original Angier, dropping him into a locked water tank where he would drown. The man who took the bow each night was a new clone, who would then live until the next performance, where he too would step into the machine and drown, continuing the cycle. The final shot reveals a warehouse filled with tanks, each containing a drowned Angier clone from a previous show—the terrible, unseen cost of his obsession. The 'Lord Caldlow' who attempts to take Borden's daughter is the final surviving clone of Angier.