Let the Right One In is as much a coming-of-age story as vampire tale, about a Oskar (Kåre Hedebrant), a shy boy who lives with his mother in a depressing apartment building located in a working class neighborhood, outside Stockholm, and meets a mysterious new neighbor Eli ( Lina Leandersson), a girl who appears to be the same age as him.

The duo exists in a severe and bleak world, where residents move between cold, sparse exteriors and compact, towering apartment complexes. Unfortunately, Oskar is constantly ridiculed by bullies, and as he gets closer to the elusive Eli, he learns that looks can be deceiving, as it is soon clear that she harbors some serious secrets. He has unknowingly befriended a vampire who was transformed centuries ago, leaving her stuck inside the body of a child. She lives in isolation with a man named Håkon who helps her obtain the human blood she needs to survive, and he struggles with his conscience to fulfill this obligation, and chooses victims whom he can physically trap, but who are not too young.   

As their relationship develops, Oskar and Eli mutually begin to navigate the perils of a unique adolescence experience, which is punctuated by moments of bloodthirsty violence, as their world around them collapses violently in this terrifying and perfectly paced reexamination of a film.