Revealing mistake: The re-use of a brief scene from the pilot episode, inserted during Nick and LaCroix's vampire battle in the warehouse, creates the unfortunate problem of Nick completely changing clothes in the middle of the fight. (00:37:35)
Factual error: The cop who arrests Nick reads him his Miranda rights ("You have the right to remain silent," etc.) But "Forever Knight" is set in Toronto. At last report, Toronto rather resolutely insists upon remaining in the sovereign nation of Canada, where the Miranda Act, a U.S. Federal law, is not observed. (00:14:40)
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.