The Corridor is a good example of what "Lovecraftian" horror should be. It's not about slime or alien things with names we can't pronounce without getting roaring drunk. Lovecraftian horror is about the human brushing up against something that defies our concept of a rational universe. In that moment humans suffer something of a psychotic break as they find themselves unable to cope with an inhuman (dare we say ahuman) universe.
In The Corridor several friends are spending a weekend in the woods. Supposedly just to have fun and guy binding, but really it's an attempt to heal. One of their numbers did have a literal psychotic break and in trying to help him several of his friends were hurt. Even though they "know" it's not his fault there is still considerable tension.
It gets worse as our recently ill character finds the aforenamed corridor deep in the woods. At first it doesn't seem much, sort of like a force field in the shape of a small room. Still, it's clearly unnatural and messes with our fellow's search for mental health. When his friends find out it definitely messes with their happy. At first I figured they wouldn't find the corridor and so the film would put the shakenly sane character against his friends. Lo and behold though they do find the corridor and as they go in the corridor grows.
Now, on face of it at this point while weird it's no more weird than say the Mystery Shack in Oregon. But there is some other force at work that grows turning them against each other as everyone's sanity is attacked. Whatever the corridor is, and we never learn really what it is at all, it seems to be trying to communicate with the men and it is turning them all crazy. The only one who's fighting against it is they guy just coming out from being crazy.
This is definitely an interesting film and worth watching. Certainly worth thinking about. Always be careful where you place your feet. One step can be the beginning of a journey.