Cape Fear-like opening: ex-convict shows up at his happily-married friend's door (someone who may or may not have been involved in the convict's imprisonment), and hauntingly inserts himself into the friend's family life. But then something awful happens, and the second half becomes the friend's slow-paced, stomach-churning revenge story, where the mood is so unbearably tense, each word of dialogue takes a screaming life of its own. Except for a few lapses (e.g., damning pictures too coincidentally discovered), this film is an unforgettable exercise in how long you can maintain the tension in drama, to elevate it to horror levels.
PS: This won the "Un Certain Regard" Jury Prize at last year's Cannes Film Festival, and currently runs a 100% score on the Tomatometer. Yep ... 100%.
PPS: It's all you again, Ali. S. Thanks a bunch.