To find the Fallout 4 All Hallows’ Eve password, first, you need to start the game after installing the next-gen update. This quest will be added to your log, but if you’re starting fresh, you’ll have to exit the vault first.
Then, open your Pip-Boy and tune in to the new Mysterious Signal broadcast under the Radio tab. Follow the signal’s marker to the Harbormaster Hotel in Boston, to the east of Diamond City.
Once there, enter the hotel and proceed to the New England Technocrat Society. Inside, you’ll face feral ghouls and eventually encounter a tough boss named Mr. Wendt. Defeat him and proceed to a hallway with numbered doors and a locked door with a keypad.
To find the password, locate Dr. Santiago, a ghoul wearing a Jack O’Lantern mask, and take it. Follow the quest marker to Lana’s Notes and read them for clues.
Each room in the hallway has specific items: Specimen Jars, Skull Candles, Teddy Bears, and Jack-O’-Lanterns. Count how many of each item you find in the rooms in order (1 to 4) to get the password.
The count for each item is 4 Specimen Jars, 3 Skull Candles, 4 Teddy Bears, and 6 Jack-O’-Lanterns. Combine these numbers to get the password: 4346.
Enter this password on the keypad to unlock the room. Inside, use the System Controls to disable the system and open the safe. Also, don’t forget to check the desk to the left of the terminal for the Picket Fences Halloween Special magazine, which adds Halloween-themed decorations to your inventory.