Let the Right One In isn’t unwatchable, but if you’ve seen either film on which it’s based (the Swedish original or the English remake, Let Me In), it’s entirely unnecessary. Demián Bichir gives a soulful performance as a father doing everything he can for his vampire daughter, but in stretching out the narrative to fill 10 episodes, it adds generic subplots that simply aren’t compelling. Crime procedural and medical research B-stories distract from the heart of what this series should be. Sadly, that flaw makes for a less-than-chilling slog that fails to justify itself when two tightly written movies of the same story already exist.