Spike first comes into the series with his love Drusilla in season two. They both were very old vampires from the 1700's, and were having a  great time terrorizing the town. Spike and Drusilla (Dru) were trying to kill Buffy since she kept getting into their way. But they had a hard time even getting near her because their old friend from way back, Angel, was protecting Buffy. 
   After Angel had one moment of pure happiness, he turned evil and joined Spike and Drusilla. It would be much easier to kill Buffy that way. But Angel keeps making moves on Drusilla and getting much more attracted to Angel. Spike decides he hates Angel for getting his girlfriend, and wants him out of their group. So Spike joins up with Buffy to kill Angel so then he can get Drusilla back. Finally Buffy and Spike are able to open a vortex, and Angel is sent to Hell. 
   Spike finally has more of a regular appearance in season 4. In the beginning of that season he is captured by Riley and the initive and gets a chip planted in his head so that he can't suck blood nor hurt a human. He finally breaks out of his prison cell in the initive and is able to live on his own. He lives underground and finds a new girlfriend named Harmony, who used to be in Cordelia's cheerleading clique. 
   In season 5 Spike gets a big crush on Buffy. She finds him disgusting and unhumanly. More toward the end of this season she starts to accept him as a "person" more.