The show stars Jonathan Groff, who you might know as Kristoff from Frozen . But there's none of that animated charm in this show. Mindhunter will reference real serial killers, like Charles Manson, but place them in a fictional story about two FBI agents, played by Groff and Holt McCallany. The two men go to different police stations and teach them how to deal with serial killers. Sounds easy enough, right?