Freddy Borden was the identical twin brother of Alfred Borden. Together, they shared a public identity as the magician known as the "Professor" and the disguise of the Professor's ingénieur, Bernard Fallon. This secret was known only by ingénieur John Cutter.
After falling out with Robert Angier due to the death of Angier's wife, Julia McCullough, Alfred began his own career as a magician under his belief that a great trick required the magician to live his act constantly. To this end, he convinced his brother Freddy to conceal Freddy's existence to assist with Borden's act and they lived identical lives. Their public identity became Alfred Borden, while the other brother disguised himself as Bernard Fallon. Both Freddy and Alfred were dedicated to their act; when Angier sabotages one of their tricks and causes Borden to lose two of his fingers, Borden cut the corresponding fingers on Freddy's hand.
For years, they succeeded in concealing the fact they were actually two men. Alfred fell in love with Sarah and had a daughter with her, Jess. Though they both shared Sarah as their wife, Freddy did not love Sarah and would even make cruel comments toward her. Sarah was not immediately aware that she was wife to both Alfred and Freddy, though she instinctively suspected that her husband was not as he appeared.
When Angier sent his new assistant Olivia Wenscombe to learn Borden's secrets, she and Freddy fell in love. Freddy and Alfred were forced to juggle their lives in order to see their respective lovers, eventually realizing Olivia's initial reasons for approaching them. When Olivia gave Borden's encrypted diary to Angier, Angier captured Freddy (as Fallon) so Borden was forced to give up the key that would allow Angier to decipher the diary. Soon afterward, Sarah hanged herself due to the strain of Borden's pursuits and learning of her husband's double identity.
When Alfred was caught and accused of killing Angier during Angier's "New Transported Man" trick, Borden was sentenced to death. Freddy (as Borden) took the fall for the accusation which had been set up by Angier to frame Borden, urging Alfred (as Fallon) to live for them both.