In Ireland, an old man working in a peat bog at night uncovers what seems to be a human body. He goes to retrieve a flashlight and when he comes back he's attacked and dragged into the murky water.
Then, we go to earlier that day and are introduced to an ill-matched couple going on a country vacation. They get stuck in the mud on a secluded road. The boyfriend goes to get help, leaving his girlfriend with the car, and comes to the house of the guy who was attacked in the opening scene. The old man had survived but has a bad neck wound. The boyfriend goes back to the car, gets his girlfriend and takes her back to the house. But the old man is crazy, infected from whatever it was that attacked him. When they shine their flashlight on him he growls and jumps out the second storey window and disappears. They are spooked so they flee, find refuge in another building and are attacked by him--and realize he's sensitive to light. In fact, he turns to stone, like a troll. Which is bad for the boyfriend because he gets bit--and begins to transform into a similar creature. This leaves the girlfriend to fend for herself against his attack...
FROM THE DARK is a well-shot, atmospheric horror movie that owes a great deal to the zombie genre. I would have liked it more if it didn't feel so familiar...