You won't be able to unlock this locked door until near the end of the game. In the meantime, keep your eyes open for the missing #6 button.
You'll eventually find it in the crypt --
-- inside the coffin that opens with the star pattern.
You'll also need to have read the note from Charlotte's bedroom about Franklin's memorial.
Where is Franklin's memorial, and what do I do with it?
Once you have the button and Nancy has commented on the dates in Franklin's memorial, you're ready to tackle the door. Click on the panel on the locked door and put the 6 button in place --
-- and nothing happens. Darn! Well, the buttons can be moved; maybe we need to put them in some specific order.
And that's where the note about Franklin's memorial comes into play. Read on.
Locked Door, Amateur
Locked Door, Master
And behind the door is someone you've been looking for. Guess who?
The person behind the door sicced a ghost on me!
What do I do after I talk to the person behind the locked door?