Truth may be stranger than fiction, but in the case of this documentary, it's an improvement. Serial killers have been a compelling subject for dramatization since Hitchcock's "Psycho," at least in American popular culture. But the fascination dates back to Jack the Ripper, and even farther back to the Middle Ages. This year it's Netflix's recent portrayal of the "good nurse" killer, a dismal excuse for biographical adaptation. It might have been worthwhile if it had offered new insight into horrible events, portrayed compelling emotions, or delved into human nature. The result could have been interesting, even entertaining, like a thriller. This documentary accomplishes all of this with no convoluted plot and contrived performances. The actual killer, Charles Cullen, is a far more chilling and impenetrable human being than the one portrayed by Eddie Redmayne. Cullen's matter-of-fact delivery as he explains the motivations that lead him to kill patients and his almost childlike self-possession are unnerving. Redmayne is a good actor, but his choice of intonation and nearly comatose performance failed to capture these real qualities. With straight-forward story telling and genuine emotion, this film imparts unimaginable horrors all the more frightening because they are so credible.