Tracy worked as a counselor for the Governor Malden. She is the sister and triplet of Niki and Barbara, which were separated at birth and manipulated genetically to give them incredible powers.
In a normal working day, and after she notice the potential of Senator Nathan Petrelli for their purposes, a reporter interrupted her routine life, alleging that she was a stripper in his past, referring to her identical sister Niki Sanders. Given that this may damage her reputation, at a time of stress she discovers her power, freezing and killing the reporter on the spot.
Tracy intends to meet with Niki Sanders in New Orleans, thus discovering that her sister died and she has a nephew named Micah. Micah helped her in finding answers, and gives the address of a doctor named Zimmerman. Upon arrival, Zimmerman confuses her with Barbara, and explains that he "created her" and gave her the powers she has. Finally Tracy didn't get many responses because Zimmerman has been erasing the memories.
Tracy felt great sorrow for the accidental death of the reporter, she tried in vain to surrender herself to the police, presenting to Nathan her resignation, and tried to commit suicide by jumping off a bridge, only to be saved by the flying Nathan Petrelli
With the discovery of the power of Nathan, Tracy doesn't feel alone, and begins a relationship with him. Gradually she accepts her powers, and learns better how to control them, to the point of siding with Arthur Petrelli (Nathan's father), for the purpose of trying to create an army of people with powers with the formula. After the death of Arthur Petrelli, her plans are finished out by Hiro, who takes the formula out of her hands, destroying it in the process.
Having returned to his life, Tracy was captured two months after the events of Volume 3 by agents of Emile Danko.
Sacrifice and lessons of morality
Shortly after the rescue of Rebel, she find out that her nephew Micah is in fact Rebel, serving as bait to catch him. In an act of sacrifice, Tracy saves Micah, creating a wave of cold, freezing herself in the process and being shot and torn to thousands of pieces by Danko.
Revival and Revenge
Tracy survived the attack thanks to her power, became more advanced and reconstructed herself from the water molecules. After surviving, Tracy was living in the sewers while she slowly sought revenge against the agents that tried to kill her. Noah Bennet was her last attempt, almost killing drowning him in his own car, but Bennet escapes and they managed to talk. She is convinced to kill no more, with the help of a moral lesson given by Micah.
Tracy tries to start her journey of redemption helping a kid with powers, Jeremy Greer, sharing her personal experience on their powers. Shortly after Jeremy is murdered, Tracy suffers moments of weakness.
Tracy begins to have serious problems controlling her powers, in an attempt to control herself, she goes to Noah's apartment looking for help. Instead she meets with Claire and they end up having a conversation about whether or not to go to the Carnival is a good option. She goes to Samuel at the end and she begins her first mission to the circus.
Tracy possesses the ability to freeze objects, which allows her to reduce the temperature of matter at will. She is capable of freezing human beings, as well as inanimate objects. While she suffers no ill-effects from the cold, she can be frozen if she uses her powers to create a very cold temperature ice wave, as shown in the episode "Cold Snap". While she at first could only focus her ability through her hands, she is later able to expand her control. As of Volume Five, her ability has developed having grown to include water mimicry, allowing her to transform into and mentally manipulate water, as seen in "An Invisible Thread".