When Faith arrived in town she came watcherless, after her watcher was brutally murdered before her eyes by the vampire Kakistos. After her predicament was discovered, the council decided to put Giles in charge of Faith until another watcher was assigned to Faith. So it was no surprise when Gwendolyn Post arrived in Sunnydale unannounced and claiming to be Faith's new watcher.

After ridiculing the slayer's methods and making Giles feel quite inferior, Gwendolyn established herself in their lives with a psychological whammy. Informing the group that she was taking over as Faith's watcher and that there was a new demon in town named Lagos who was searching for the "Glove of Myhnegon". She also told Giles that one of her duties was to send a report back to the council on Giles' performance because they felt he was becoming too "American".

Taking the lead, Gwendolyn suggested that the slayers together should kill Lagos and track down the glove. But other things are happening that only Buffy is aware of…Angel is back. After Xander discovers Buffy's secret the scooby gang (minus Faith) decided to do an intervention with Buffy to find out exactly what is going on. Gwendolyn, who has some darker plans of her own, went to Faith's apartment to help her train as well as sow some seeds of discontent in the unstable girl's mind by informing her of the meeting and reminding her that she wasn't included as part of the core group. But mainly what she was trying to do was make Faith loyal to her and her only. You see, Gwendolyn Post wasn't exactly what she was making herself appear to be. Yes, she was looking for the glove, but to her own ends. It seems that Gwendolyn had been kicked out of the Watcher's Council a few years previously for misuses of dark power. Gwendolyn was power hungry. She knew that if she got the glove she would be an unstoppable force but she wasn't naïve enough to think she wouldn't need help. When Giles told her that the Glove was at Angel's house she knocked Giles out and went in search of it. But Giles didn't tell Gwendolyn that Angel was a vampire, so when she tried to kill him with a blow to the head he simply went unconscious. When he came to he was vamped and ready for action…but by this time Faith had shown up believing that Giles' injuries were from Angelus and she was ready to kill him. Gwendolyn fed her with Faith's own mistrust and while Faith battled Buffy and the others Gwendolyn managed to get the glove out of Angel's locked trunk and put it on. Once on the glove attached itself to her arm and she had the power of lightening.

Faith realized Gwendolyn's treachery a little too late. But Buffy saved the day by shearing off Gwendolyn's arm with a piece of broken glass. Unfortunately for Gwendolyn she was destroyed by a stray bolt of electricity and incinerated.