'While You Sleep') is a 2011 Spanish psychological thriller film directed by Jaume Balagueró from a screenplay by Alberto Marini which stars Luis Tosar alongside Marta Etura.

In the film, César (Tosar), a concierge of an apartment building, is unable to reach happiness no matter what happens to him, and he has a goal to make the tenants upset.

Clara (Etura) proves to César that making her upset is harder than he expected and things turn to a twisted event when her boyfriend Marcos visits her.

As he wakes up in Clara's apartment and begins his routine working in the main lobby, he gives hush money to teen Úrsula, the daughter of another tenant.

Visiting his mother at the hospital again, César says that he is close to wiping Clara's smile off her face as his goal is to make his tenants miserable.

Clara has moved out of the apartment and had her baby, César mails her a letter hoping that any time she looks at their child she will think of him, and he thanks her for helping him finally be happy.

Balagueró stated that it was a challenge to have story in point of view of the villain and not the victim, hoping to establish a morality play that would make the audience a necessary participant.

[13] Sleep Tight had its world premiere at the Fantastic Fest in September 2011,[14] followed by a screening at the 44th Sitges Film Festival on 8 October 2011.

[19] The review-aggregation website Rotten Tomatoes gives the film a 94% approval rating based on 31 published reviews—a weighted average of 7.3 out of 10.

[21] Jonathan Holland of Variety had positive comments about the film stating that Sleep Tight "designed to give audience sleepless nights, and mostly succeeds".

[22] Simon Crook of Empire had similar comments to make stating that the film is "old-school, simmering with Hitchcockian suspense, but even the most hardened horror-heads will find its after-effects hard to brush off.

"[24] Manohla Dargis of The New York Times had mixed reviews claiming the chilly film works at first but that Balagueró "is so overtaken by his villain that he becomes like César, displaying an eagerness to play the role of tormentor, which kills both the movie's pleasure and its flickering political subtext.