Skye Winters is the younger sister of Traci Winters, the title character in the series Traci the Vompire Hunter and Guardians. Skye first appeared early in the final episode of season 4, slipped in without any formal introduction. Traci awakens to find her living in her house.
In the opening episode of season 5, Skye: Part I, Traci realizes that she is the only one who sees anything odd about Skye. Everyone else accepts her as Traci's sister. Traci shared her knowledge with Gereint who knew better than to doubt Traci's intuition. He advised her to keep this fact secret, and began intensive research in his library.
Traci noticed other oddities. Vompires she'd killed turning up alive, a few street names being different, even a different General Moderator. In addition, people react oddly to Traci's casual behavior, and the Staketeers are far less friendly with her. Sharing these facts with Gereint, he discovered the truth. She was not the Traci he knew. Somehow, Traci had slipped through an interdimensional portal into a parallel world, being exchanged with the Traci of that world.
In episode 5:2, Skye: Part II, Gereint and Xandra figure out how to return our Traci to her world. At last, they work out the spell, and Traci returns to her world. In her own world, Gereint and Xandra had done the same thing. The two Tracis are returned to their original worlds. However, for reasons which weren't, until mid-season, explained, Skye also found herself in our world.
Traci came home to find Skye waiting, alone and bewildered, confused about her room having become a storage closet. Traci explains what happens, and assures her that they would do their best to figure out why she'd come along with her, and how to return her to her own world. Traci later explains what had happened to her mother. They decide to tell people that Skye was an out-of-town cousin who was visiting for an extended period.
Meanwhile, in the alternate world, Alt-Traci has returned to find her mother alarmed at Skye's disappearance. She tells her all about what has happened, and, like our Traci, assures her they'll figuer out what had happened, and how to reverse it. It is unclear how Skye's absence was explained in the alt-world.
In episode 5:10, Skye wakes up in the middle of the night from a horrible nightmare. She woke Traci up to tell her what she'd seen. In her dream, a powerful demon had killed Traci (or rather, Alt-Traci), her mother, and the Staketeers. Traci suspected that it was more than just a dream, but rather, a psychic vision.
As the season progressed, Skye had more and more visions of the apocalypse unfolding in her world, until at last, she discovered that the demon responsible planned to cross over to our world, an unleash a new apocalypse.
The first demons from the alt-world appear in episode 5:21. After a desperate battle, in which Traci nearly dies, the demons are at last beaten back, and a seal is placed upon the altworld, confining the evil there.