On the Blood Path

Open Door / Search Guard Station for Key: First things first, you'll need to accept this mission from Ramsden. Once you've got it, head to the waypoint on your map and open the door. Inside, your main goal is to find the Prison Gate Key. The game says there are three possible locations for it, so you'll need to search around. The guide mentions looking behind a crate as one of the spots.

Unlock Gate / Find Holder: Once you've snagged that key, make your way to the next waypoint and use it to unlock the gate. Get ready for some action – you'll need to take out all the enemies inside this area. After you've cleared them out, head up the stairs towards the back of the area to find Holder's Cell. Flip the switch to open it up, and then interact with the body inside. Surprise! It's not actually Holder. Keep your eyes peeled on the floor to your left; you'll find something you can interact with that opens up a secret path downwards. Drop into this hole and follow the path until you reach an open room. More Shanks will be waiting for you here, so deal with them. Once they're down, you can finally speak with Holder at the back of the room.

Side with Holder or Ramsden / Kill Holder or Ramsden: After you've dealt with the Shanks, you'll have a chat with Holder, and this is where the choice comes in. You can either side with Ramsden or Holder. Honestly, the guide says it doesn't really impact anything, so pick whoever you like! After you've made your decision, you'll need to take out the person you *didn't* side with. Then, just speak to either Ramsden or Holder to wrap up the mission.