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As Connor (Vincent Kartheiser) continues to care for -- and flirt with -- the amnesiac Cordelia (Charisma Carpenter), Fred (Amy Acker) faces her demons, both figurative and literal. After five years as an other-dimensional slave and another two working with Angel Investigations, Fred is delighted to get back into the academic realm with the publication of a paper she's written about quantum physics. But at the symposium where she's been invited to deliver her findings, an enormous demon foe crashes the party through a mystic portal. Angel (David Boreanaz) and friends fight off the beast, then follow its trail to the local comic-book store, where Angel is excited to learn that he's something of an underground sci-fi sensation. Fred, meanwhile, makes a less delightful discovery about Professor Seidel (Randy Oglesby), the scientific mentor who has just stepped back into her life. Fred learns that it was Seidel, threatened by her scholarly abilities, who engineered the original portal that sucked her into the demon realm of Pylea years ago. The normally pert and unassuming Fred resolves to kill the man who ruined her life, and she turns to tortured former teammate Wesley (Alexis Denisof) for assistance. Just as Fred is about to execute Wesley's plan to kill Seidel, her boyfriend, Gunn (J. August Richards), shows up to beg her not to take a human life. Certain that Fred would never be able to live with herself, Gunn himself snaps Seidel's neck just as the doctor is being sucked through yet another demonic portal. Fred and Gunn's budding romance is clearly past the carefree phase. Originally broadcast November 3, 2002, on the WB network, "Supersymmetry" marked season four, episode five of the supernatural comedy drama.