Weird West: Definitive Edition

Missable.
During the Copper Mountain Quarry mission at the end of the Gun Slinger prophecy. You'll have the choice of unlocking one of two missable achievements. The "Great Escape" or "Out on the Ebb Tide" - however if you save in the right place you can get them both!

Firstly lets get you to a good save point. The Quarry is fairly linear, clear all enemies and collect any loot you require. You don't need to be quiet or stealthy. If you come across any "levers" leave them alone for now, these are used to unlock Shelby Cross's hidden door for the "Out on the Ebb Tide" achievement. When you reach the end of the quarry you'll find your spouse trapped - lower the draw bridge to release him and a quick dialogue will play out. Once the dialogue has finished I suggest saving here! With the quarry cleared and levers untouched. You can revert back to this save later to get the second achievement.

Now to get "Out on the Ebb Tide" you have to open the hidden room in which Shelby Cross is hiding by pulling three fairly hidden levers:

1. In the large open room with water on the ground, high up on a ledge in the corner by the entrance. I suggest using a barrel to reach this ledge - you might need 1 or 2 points in jump to reach it.

2. To the right of Shelby's secret door is a room with a few cells. The lever is sat in plain sight and easily pulled.

3. At the end of the Quarry by your husbands cell. From his cell you can jump to the outer most wall and walk round to a red curtain. Behind the curtain is the third and final lever.

Now with the door open, head through to kill Shelby. I suggest keeping to the right and sneak round the back of him. He's much easier to kill when unconscious :D - once killed the achievement should pop.

Top Tip: Do "Out on the Ebb Tide" first and then revert the save to do "Great Escape". This way Shelby Cross is still alive when you move onto Chapter 2. Shelby will then appear on bounty boards for the "Elusive Prey" achievement.

See my video guide for more detail:

During the main story, after you've found , there are three levers you need to interact with to open a certain door in the inner sanctum.

The first lever is behind the cage mentioned and you need to jump across to a ledge from inside the cage to reach it. It'll be behind a red curtain.

To find the second lever, backtrack to the inner sanctum main room, where the door you want to open is, and face the blue stairs to your right. Instead of going down the stairs, follow the path beside it (there should be rubble you walk through. The lever is in the left corner of the space.

The third and final lever is in the big flooded room (if you continue through the room from the second lever, you'll reach it). Follow the broken rail until you get to the point where it turns left. You'll see a pillar next to a piano in the water to your right. Update by user Uncompressed - you can apparently simply shoot this lever (my original solution is below).

Jump onto the pillar and in the corner, you should see the final lever propped up on a ledge. You should be able to jump across from the pillar (I had the jump upgraded twice).

From this point, simply head through the door in the inner sanctum that will now be open and follow the path. You'll find the target inside a fancy hall at the end.

Hope this helps!

The other guides have done a good job telling you what you need to do to accomplish the achievments. I do have something helpful to add though. And I discovered it completely by accident. You can unlock The Great Escape and Out On The Ebb Tide in the same playthrough without having to save and restart. When you get to the final room where Shelby Cross is if you enter in stealth mode and wait until Shelby sits down at his desk and Tammy is looking in another direction. You can sneak up behind Shelby and render him unconscious with a choke hold using RT. Tammy will immediately aggro if she is close by. Take her out. Then you can take Shelby out while he is still unconscious. This will get you Out On The Ebb Tide. Then once you leave the quarry you will get The Great Escape. I am guessing it is because by stealthing in and never being detected, you thus never alert Shelby before you knock him out which meets the requirements for The Great Escape.