<P> Season four sees Buffy and Willow enroll at UC Sunnydale while Xander joins the workforce . The vampire Spike, having been left by Drusilla, returns to Sunnydale and is abducted by The Initiative, a top - secret military installation based beneath the UC Sunnydale campus, led by Maggie Walsh . They implant a microchip in his head which prevents him from harming humans . He reluctantly helps the Scooby Gang throughout the season and eventually begins to fight on their side after learning that he can harm other demons . But Buffy and her friends don't trust him except Willow who opts to give him a chance to redeem himself, which they eventually do . </P> <P> Oz leaves town after realizing that he is too dangerous as a werewolf and after a horrific encounter with The Initiative . Willow falls in love with Tara Maclay, another witch . They begin a relationship . </P> <P> Another focus of the season is Xander's relationship with a former vengeance demon named Anya Jenkins, who becomes infatuated with him due to him making her feel human and Xander returns these feelings as she makes him feel like a man . Anya tries to get Xander off her mind but their feelings are developed and they begin a relationship . </P> <P> Buffy begins dating Riley Finn, a grad student who she later discovers is a member of The Initiative . He tries to get her recruited but she becomes an object of negative attention from Maggie Walsh . Walsh believes Buffy to be a bad influence to Riley, threatening his ties with The Initiative . After Buffy and Riley's first sexual encounter, Walsh tries to get Buffy killed, which causes Riley to cut ties with Walsh and The Initiative . </P>

When does angel come back in season 4