Forest is the last level. You have to find a building - it's also on the map - where inside you can see inscriptions and a doll, which is a key.
In the room around the inscription you can find all four remnants, so it's enough to find this place to finish this level.
Exit - Level 4 - Forest - Storyline - Daylight - Game Guide and Walkthrough
Exit gate is easy to find. It's a narrowing of the map.
Behind a gate, you see scaffold. Beware, as the water will kill you if you fall into it. On the first wall on left you see a note.
Another secret can be found on the other side, on the higher level of the scaffold on which you get using chests.
In the middle, you see a letter on one of chests. You have to jump to the water and quickly onto the chests to not die.
One more envelope is at the bottom, attached to the construction.
Move forward on scaffold. You'll see a coffin - behind it, on left, there is a note attached to the wall.
The last but one remnant is in the right corner of the scaffold.
When you get down from the scaffold, head for the mansion in front of you. There is an open passage.
You're in the safehouse. Find a room with a desk in the middle of it. After listening to the recording, you have to run until you notice stairs. Then you'll be almost surrounded by Shadows. You have to get to the highlighted exit ASAP.