The Games Vampires Play - S3-E15
Factual error: At the end, Nick recites the "you have the right to remain silent" spiel to Rita as he arrests her. Suspects in Canada, where this show is set, are not "read their rights." That's a U.S. law (the Miranda Act) and it isn't observed north of the border. (00:41:45)
Answer: Nick was sick and tired of being an immortal bloodsucker. He wanted to be human, fall in love, get married, have children, grow old and die. As for Janette, according to her, she fell in love and the passion she felt "cured" her of her blood lust.