Vault 75 (quest)

Vault 75 is a side quest in Fallout 4 which is triggered when exploring Malden Middle School.

Detailed walkthrough
In the basement of the Malden Middle School, go through the vault door and enter the elevator going down. Keep going a one way direction until encountering a door to the lab on the right-hand side that needs an access card to be opened.

At the end of the hallway, you will get to the atrium. Go forward and turn right into a locker room to see another hallway and inaccessible door to the lab from the other side. Go left, down the stairs and left towards a diner. Go into it and upstairs and get the access card from the tool case.

Make your way back to the second blue door and open it with the access card. The door in front of you leads to the first blue door, it's just around the corner, left.

Go up the stairs and you will find yourself in a room going three different ways; go forward. Kill the Gunners and get the admin access card from one of them. Now you should be in a room with a view to the diner you've been to previously. A bobblehead is on one of the tables.

Backtrack to the lab room and use the admin access card on the door. Climb up a few stairs and you should be in the overseer's room. Activate the terminal on his desk to complete the quest.

When you enter the overseer's room, on your right is his bedroom with a Grognak comic on the bed.

Bugs
Even after completing the quest, you may not be able to remove the Vault 75 access cards from your inventory, as they will still be flagged as active quest items.

Vault 75 (quest) Убежище 75 (квест) Сховище 75 (квест)