Daphne Millbrook was Matt Parkman's love interest in Volume Three. With the ability to run at super speeds she was perceived by Hiro Nakamura as being a villain, when in actuality she was being used by Arthur Petrelli.
Before her powers manifested, Daphne suffered from cerebral palsy requiring her to need leg braces at all times. She grew up in a corn field in Lawrence, KS. Knowing only a life of crime using her super speed to steal for money, she is hired by Arthur Petrelli to steal the half of the formula from Hiro and Ando, to be dubbed Nemesis by Hiro.
In a future seen by Matt Parkman, Daphne and Matt live in Mohinder Suresh's old appartment in New York, with Matt's turtle and Molly Walker. Daphne was killed in this future by Sylar using his radiation going out of control over the death of his son. She attempted to run away from the blast and made it back to New York, only to realize she couldn't outrun the blast and died in Matt's arms, as Matt dreamt when he was using Usutu's power in Africa.
Her power of super speed allows her to run at high speeds which should allow her to run on water which would make sense since she ran from Paris to pinhearst in NJ. it's discovered in Dual that with Ando's new ability, she's able to run faster than the speed of light, allowing her to time travel.She was able to move even whilst in time paralysis caused by Hiro.
After being shot in the arm while trying to help Matt Parkman, Claire Bennet and Mohinder Suresh, Daphne was left for dead and taken by government soldiers. She was believed dead but was really drugged and kept in a secret facility by Emile Danko and his cohorts.
Later, an angry Matt discovered that Daphne was not dead but was just apprehended. He tried to save her to no avail.
In Cold Snap, when Rebel freed Tracy Strauss, she then freed Mohinder, Daphne and Matt. The men rushed Daphne to a hospital after splitting ways with Tracy. There, Matt lied to the doctors and told them that Daphne was his wife, Janice Parkman, and that she was wounded in a hunting accident. Sometime later, Daphne awoke and noticed that she was surrounded with cards and balloons saying "Get well Gwen Stefani".
Daphne and Matt then had a conversation about their relationship and Daphne decided to call it quits. She then left. Towards the end of the episode, Matt discovered Daphne on an unknown rooftop and began to try to persuade her to like him still. He told her that he could fly and demonstrated the power. Daphne then asked Matt to fly her. He did. In midair, Daphne told Matt to let her go. He told her no and then she told him to fly her to the moon if he could. The duo then flew to the moon.
After all of that had happened, it was revealed to viewers that Daphne never woke up in the hospital room. She had actually passed away and all of the things that she had done and seen were compliments of Matt's telepathic abilities.