Sydney "Syd" Barrett was born and raised in an urban area. Her mother was a successful essayist who was married many times. At some point, Syd discovered that she was a mutant with the ability to mentally swap places with anyone she touched.
Syd was admitted to the Clockworks Psychiatric Hospital, where she met David Haller. David was diagnosed with paranoid schizophrenia, but was actually a mutant with powerful, uncontrolled psychic abilities. He became Syd's boyfriend during her time at Clockworks. However, she made sure David would not touch her out of fear of activating her powers. When Dr. Kissinger cleared Syd to leave the hospital, David kissed her goodbye, causing them to trade places. Syd was unable to control David's powers. The "devil with the yellow eyes," a figure that haunted David's visions, appeared and dragged the hospital's patients through the walls back to their rooms. Lenny Busker, one of the patients and a close friend of David's, was killed when she wasn't dragged completely through the wall.
The sudden surge in power caught the attention of two organisations, friend and foe. Syd was intercepted by a group of other mutants, led by Melanie Bird. David, on the other hand, found himself in the custody of Division Three, a government agency that captured and studied mutants. When Syd learned this, Dr. Bird gave her permission to lead a mission to rescue David. Accompanied by fellow mutants Ptonomy Wallace and Kerry Loudermilk, Syd found David and brought him to meet Dr. Bird. 
David and Syd continued their relationship as David began learning more about his powers with Ptonomy and Melanie. Hoping to get a better understanding of how David's mind and powers worked, David was placed in an MRI machine, which he destroyed when he received a vision of his sister, Amy Haller, being abducted by Division Three. David prepared to leave in order to save his sister, but Syd convinced him to stay, assuring him that they would come to Amy's rescue after David had developed better control of his powers.
Back in the MRI, David received another potent vision that literally shook the building. Syd entered the MRI room to help David, and the pair's psyches were transported to the facility where Amy was being held captive. This was cut short when one of the agents, a man dubbed "The Eye", apparently noticed the pair of them. Syd and David vanished, manifested back in the physical world and explained to Melanie what they had seen. Melanie recognized The Eye as Walter, another mutant and former friend of Melanie's husband Oliver. Melanie requested that David be sedated temporarily so she could have unfiltered access to his mind so get a better understanding of his powers.
Reluctantly, David agreed, and Syd agreed to enter his mind alongside Ptonomy, David, and Melanie. The sedation kept David's rational mind from entering the memory landscape, and so he manifested as a young boy. Since Syd's powers did not work outside the physical world, David and Syd were able to embrace for the first time. In David's mindscape, Syd received an unsettling feeling and asked Ptonomy to return them to the real world, but he was met with a similar force of resistance. David's boyhood self ran away, and Syd gave chase throughout a series of memories, and the pair found themselves reliving the same nightmare from David's MRI -- cornered by the angry boy, who then transformed into the Devil with the Yellow Eyes. Syd urged David to wake up, and Syd and Ptonomy were able to return to reality. Melanie forcibly awoke after an encounter with the yellow-eyed demon, but David remained under, which worried Syd intensely.
Powers and Abilities
Sydney Barrett is a mutant.
Consciousness Transference: Whenever Syd touches another person, her mind enters the other person's body and vice versa. While temporarily in the other mutant's body, she takes on their powers. After some time passes, her's and the switched subject's body return to the proper person. The body transformation occurs instantly, and presents as a sudden transformation for both parties, wherever they may be.
Unarmed Combat: Syd was able to fight off numerous government soldiers without any weapons.
- Rachel Keller portrays Syd Barrett in the television series Legion. Keller worked with Legion showrunner Noah Hawley in the second season of Fargo.
- The character is named after Syd Barrett, a founding member of the band Pink Floyd.
- As revealed in Ask Marvel: Katie Aselton and Rachel Harris from Legion on FX Syd doesn't like cherry-flavored food, although she ate cherry pie in an illusion projected by David.
- 24 appearance(s) of Sydney Barrett (Earth-TRN620)
- 1 minor appearance(s) of Sydney Barrett (Earth-TRN620)
- 1 mention(s) of Sydney Barrett (Earth-TRN620)
- 19 image(s) of Sydney Barrett (Earth-TRN620)