Find a cipher in Twin Elms

The correct order is

Right, Middle, Left, Right

Alternately, you can find a key in the same room where you found the clue that allows you to bypass the whole thing.

There's actually a Unique Pistol available right on the very first map of the tutorial section of the game!

To find it, you'll need to have at least 1 point in Mechanics Skill after character creation. That means you'll need to be playing as a Cipher, Chanter, Rogue, or Wizard, OR, you'll need to select the Laborer, Merchant, or Scientist background. Any one of these options will give you at least one point of Mechanics.

Then, after you've been assigned a bodyguard and told to go look for berries, head for the far Southwestern corner of the map; the weird campfire, across the bridge near the stream:

Once there, take a closer look at the tent - you'll need to turn on Scouting Mode (i.e. Stealth), and move around in the area a bit - soon your character will notice something, and a new (hilit in purple when you tab hilight) container will appear:

You'll find The Disappointer! It... lives up to it's name, unfortunately: