The hidden bunker room combination lock puzzle in The Medium might not have a simple solution at first glance. However, there are clues in the world that drop big hints about working out this conundrum.
It should be said that there are story spoilers from this point on. If you haven’t come across a cutscene involving Sadness on a swing, turn back now as we discuss some plot details here.
After you gain access to the Red House’s basement following some back and forth action between the real and spirit worlds, head downstairs and drop down into the underground area. If you walk straight ahead and squeeze through the gap in a brick wall, you will come across the hidden bunker room. There is a combination lock device to the left of the door, and you need a four-digit code to unlock it.
Head back into the main basement room. Walk across to a room on the back left wall. You will find a paper receipt on a table immediately to your right, and a locker next to it. Open the locker using your bolt cutters.
There is a box for Thomas’ pocket watch in here. Pick it up and read the inscription. The watch was given to Thomas by his wife for their 10th anniversary. Remember this as you put the box back. Now, inspect the paper receipt on the table.
It reads that the pocket watch was purchased in 1976. Take ten years off that year, and you will have 1966, which is the year that Thomas married his wife. Go back to the hidden bunker room lock. Enter 1966 into the device using the nine-digit options, and the door will unlock.