You begin this chapter in the basement as Sam. At first turn back since next to the door are the Death Machine plans. On your left you may find the cupboard with the Josh's cellphone. In the desk drawer on your right you will see the psychiatric report. Camera will change in this room. Turn left toward the boxes. Move them to find the remembrance board.
Move forward through the corridor. Get to the locked door and to the stairs. In the depression on your left you will find a desk and the voice recording (you need to listen the entire thing to get this clue). Now get upstairs and pass the double door. You will find the dummy in Sam's clothes and the video camera. After few moments you will see Mike. Open the blocked door for him.
After a short cutscene you will start playing Emily. At first you need to get to the save place. Walk forward until you get to the huge locked door. To open them you need to go up the tracks where you will find the wagon which you may release. Left of it you may find a chest with the miner photo. In the last scene you need to try to escape with the elevator which is impossible since the power is off. Before moving forward find a new clue while interacting with the clocking-in machine right of the elevator, next to the wall.
Walk deeper into the corridor. In the end you will find the Death Totem#5. Use the ladder which Emily will fall off. You need to make a way out through the blockade made of wooden boards in the end of the road. You will get to the big room in which you may find the miner's family photo in the upper right corner in the orange container. Try to climb up the rock ahead. The choice about the way is not important since you just need to deal with some QTE. After a while you may get to the power switch.
Leave the stairs and go to the barrel on your left where you will find the Danger Totem #3. Get to the area where you may find opposite of you: the Hannah's glasses, on your left: the marks on rock hidden behind the boards, on a barrel on the bottom of the screen - the tattoo photo. Later on in the right part of the corridor you will find the Beth's cross and on a barrel in the end of the corridor: Hannah's medallion.
Pass the corridor and move the gate. You may find here the Beth's head, the last clue from this area. After few moments you will return to the room with the elevator which is now. You will be unable to use it but instead a man with a flamethrower will appear. Beside of your decisions during the QTE you can't escape from him (however you may hide).
Warning - hide during the last decision, when your only other option is to return. It is the only way to collect one of the collectibles during the eighth chapter.
The last scene of this chapter is a short cutscene with some not very significant dialogue options. You will speak as Chris and you may be acquiescent towards either Mike or Josh. It will update the butterfly effect (And Which One Will Die).