Planting the explosive | Mission 1 - Dishonored Dishonored Guide
Last update: 11 May 2016
New Main Quest: Cross the yard
Exit the interrogation room and note that one of the Guards opened the door to the prison's main yard (the above screenshot). Go there and enter [Prison Yard]. Go down the stairs, hide behind one of the pillars and wait for the opponents' conversation to finish.
You may have already noticed that one of the guards positioned himself to the right, whereas the other one is patrolling the yard and stops briefly here and there. If you want to avoid the guards you should take the path to the right shown in the above screenshot. This way you will easily reach the stairs. If you decide otherwise, deal with the stationary guard first and after you hide his body, turn your attention to the other one. There is nothing interest worthy in the yard, apart from a small amount of gold, although one of the guards has a yard key on him.
You can reach prison's next location in two ways. You can either climb the stairs mentioned earlier (the above screenshot), or return to the starting point and use the yard key (the one stolen from the guard) to open the door located near the cell that was earlier occupied by Corvo. In my opinion, however, this is not necessary. Either way, you will get to [Control Room Section].
New Main Quest: Enter the hallway leading to the outer door
The last area of the prison can be reached in two different ways. Variant one assumes using the pipes adjacent to the wall on the right of the room you are currently in. Wait until the guards disperse and go right hiding behind objects on your way (the above screenshot). Find the place where you can start to climb by jumping from one pipe onto another.
Reach the highest pipe and go towards your current destination. After you reach a new area it is up to you either to jump down somewhere in a safe spot (e.g. the balcony to the left that is occasionally occupied by one of the guards) or land on the guard visible in the above screenshot and execute him (by pressing left mouse button right before landing).
Variant two assumes opening the gate that you can see in the distance. In the case of this variant, I suggest dealing with the guard patrolling the corridor first. You just need to make sure that you do it out of anybody's sight (the above screenshot). Traditionally, you need to drag the unconscious or killed guard into a darkened spot.
Now deal with the two guards occupying the side rooms. Start with the one located the closest to the starting point and enter it only after the guard turns away (the above screenshot). Next, peek through the keyhole and enter the neighbouring room at the right moment to deal with the last of the guards.
After you deal with all of the guards, it is a good idea to explore side rooms for gold, food, ammo and Sokolov's health potion. Then intereact with the switch located in the second of the side rooms. Warning - if you do not want to attack guards, you should immediately make use of the door leading to the room with the switch, being mindful of course, of the last of your enemies' actions.
New Main Quest: Plant the explosive
There are two characters between you and the wall that you need to plant the explosive on. The first one of them is standing at the gate (the above screenshot). If you are on the lower level, you need to attack him and drag him away into a dark location, being careful, at the same time not to get within the sight of the other one of the enemies. If you are on the pipes on top, you may either jump down onto the guard or avoid him by choosing pipes leading to the balcony on the left.
The other one of the guards is patrolling the upper balcony and the area near the wall you are trying to approach. Regardless of your position (lower level or the pipes) you may get him from behind and neutralize, or try to avoid him. In the case of the latter, I recommend turning your interest to the objects that you can hide in, like a crate or a trash container.
If it's possible explore the area to find food, ammo and Sokolov's health potion. You can also use the switch to close the gate, which will make it a bit easier to avoid guards after the explosion occurs. The last thing to do is plant the explosive on the marked wall (by pressing "F" key).