The "Mastermind" achievement is obtained by seeing all of The Visitor's memories throughout the game. About half are tied to story progression, with the other half being entirely optional. You can collect these in any order, and none are missable, so you can collect these as you play, or get them when you're nearing the end. Obviously, since several of these are tied to story progression, this guide will contain spoilers, so do not read further if you wish to avoid any story or puzzle details.

The first memory can be found in the Waiting Room, to the right of Julia's desk on the first floor. The memory is triggered by clicking on a small calendar labelled "June" next to the door that leads back to Julia.

The second memory can be found once you fix the lights in the basement. Return to the room that you found the wire cutters in, and you will see a boarded up wall. To the left of the boards is a pickaxe sticking into the ground. Click on the pickaxe to play the memory.

This memory is unskippable because it is tied to story progression. The third memory is found in room 102A, Betrand LaRouche's room. There is a chessboard on a nightstand on the left side of the room. Click on that to see the memory.

This memory can be found in the Therapy Room. Click on the circle of chairs in the center of the room. You may need to stand next to the projector to get it to trigger.

This memory is quite easily to miss, since it is in a part of the asylum that isn't even marked on the map. On the second floor, past the the operating rooms and Hydrotherapy, you will find the corridor that would lead to the Female Hospital, though it is inaccessible. To the right of the door to the F. Hospital, is a wooden walkway. The memory will play as soon as you step into this walkway.

This memory is unskippable, because it is tied to story progression. After reading the notes on Dr. Hanwell's desk, exit his room. This memory will trigger as soon as you exit into the hallway.

This memory is unskippable, because it is tied to story progression. In the museum, place the correct tissue sample on the glass slide. Afterwards, leave the Museum. This memory will place when you enter the hallway.

This memory is unskippable because it is tied to story progress. After conducting the biopsy and using the microscope, exit Operating Room A. This memory will play when you enter the hallway.