Doctor Who (Season 3, Episode 10), "Blink"

This episode follows Sally (played by Carey Mulligan), a young woman who explores an abandoned house with her friend Kathy. Sally finds unnerving messages addressed to her specifically underneath peeling wallpaper, and suddenly her friend mysteriously vanishes. Trying to find some answers, Sally is left with only the help of Kathy's brother and cryptic DVDs from a time traveler warning her of the growing danger around her, and time is not on Sally's side.

This is one of the best pieces of television I've ever seen. It's a great entry point into Doctor Who, but it also stands incredibly well on its own. If you like an intriguing mystery and a tiny, baby-sized bit of horror, I feel like this scratches that itch!