First Floor

Outside

The carriage rails deposit you right outside of the front doors of the Addermire Institute. As you approach the front door, watch for guards on your left. They'll finish their debrief, and then one will pass to your right. Wait a couple seconds, then you can follow him over and knock him out.

When you approach the front doors, turn to the left. There's a guard office there. The guard inside has his back to you for now, but that won't last. Sneak in and take him out so he doesn't become a problem later.

Main Entrance

Sneak inside the front door (and grab the bonecharm), then cut to the right. You can Far Reach up to the second floor here. Hop up and disable the wall of light — and check out the office up there to grab the blueprint.

Disabling the wall will trigger the guard to start patrolling. Use the chandeliers to stay above, then knock out the guard with a drop attack.

Before you go charging anywhere else, there are two more guards to deal with. The first is also patrolling the floor, closer to the dining room. He can also be handled from above. The second is sitting in an office to the left of the wall of light. Stay up on the chandeliers and use the pipes that pass over the office to get the drop on him.

Now you can pass through the wall of light — make sure to grab the painting on your right. Just through it, you'll see the map of the Addermire Institute. Be very careful here. A guard will arrive in the elevator and ruin your day. Stay crouched and duck to the left side of the elevator shaft. Wait for him to pass, then get take him out. Stash him under the stairs so no one spots him. Now you can examine the map freely. You'll be referring back to it periodically to keep your bearings while you're going up and down the floors.

From here, turning left will take you to the dining hall — which is full of guards — and turning right will take you to a barracks and kennel wing. Feel free to explore them both, but neither are necessary to your mission. Start up the stairs.

Fourth Floor

Dr. Hypatia's Office

Your goal right now is Dr. Hypatia's office on the fourth floor, but you've got some ne'er-do-well guards playing dice on the landing between three and four that will get in your way. First, make sure you're crouching so you don't make any noise. Then Far Reach onto the chandeliers until you're just above the guards. Take out the left one with a sleep dart. You can also take out the other one with a sleep dart, but he sometimes falls into their lantern and you end up with an Uncle Owen and Aunt Beru situation. It's safer to pounce on him.

Continue slowly up from the third floor to the fourth. As you come around the elevator, you'll see two guards talking at a desk. Back down the stairs a little and be patient. The blue-shirted guard will exit to the terrace through the doors on your right. The red-shirted guard will follow shortly.

With them out of the way, you're free to explore Dr. Hypatia's office. Pick up everything you can, but your primary goal is the key on her desk.

Collectibles

Exiting through those same doors the guards went through is a great way to access several of this level's collectibles — including the elevator you have to break to get into the basement — and it's not well patrolled. There's nothing mission critical out here, though, so we'll leave that to the collectibles guide.

Third Floor

Recuperation Room

Now that you've got the key, head back down to the third floor. Turn to the right to enter the Recuperation Area. This area has clearly seen better days. Fight your way through the blooflies using the conveniently provided incendiary bolts and flammable bottles. Pick up the bonecharm in the office in the center, then head through the door in the back right corner.

Dr. Hypatia

This will lead you to a level above an open laboratory below you. Drop down and talk to Dr. Hypatia. She's clearly not all there.

After she's done being generally creepy, head into the office on her right for a few more details (and collectibles).

There's a hallway on the opposite end of the room from Dr. Hypatia. Get back there to talk to Vasco. He'll confirm what you're probably suspecting and give you the directions to create a cure — this is the non-lethal solution to the Crown Killer problem.

The conversation doesn't end well, but you've got your next objective(s).

Second Floor

Vasco's Office

Your HUD markers will lead you to Vasco's office. It's on the second floor in the Disease Treatment wing. You're going to pass by Joe Hamilton, so now's a good time to grab his key (which you can use to pick up a blueprint in his office on the fifth floor). Watch for the blue-shirt in the hallway. He'll be focused on Hamilton's room, so you can get behind him easily.

There's a red-shirted guard patrolling at the end of the hall. Follow her into Vasco's office and knock her out.

Use the combination Vasco gave to you open the safe and get his notes.

Then head into the lab on the right to create the anti-serum.

Third Floor

The Crown Killer

Follow your HUD's marker back to the Crown Killer. Chances are, she's in the same place you left her. Use the balcony's railings and beams to get the (literal) drop on her and use the serum you made to save Dr. Hypatia.

First Floor

The Watchtower

Before you can leave, you have to disable the watchtower. The easiest way to do this is by cutting through the dining hall. After saving the eponymous good doctor, head back to the main stairs and take them down to the first floor. Stay crouched and slowly work your way inside. Keep to the left and use Far Reach to skip past the diner's awareness. There's a door in the back right corner that will lead to an exit.

There are two guards outside. Turn right as soon as you walk out and climb over the boxes. Take out the blue shirt first, then turn your attention to the captain.

This lets you hop straight onto the Watchtower and disable it.

Continue the rest of the way down to the ground and take out the guard there. Now you can board the skiff with Meagan and finish the mission.