After taking control of your character, approach the hole in the wall and eavesdrop on the conversation of your fellow prisoners. When they finish talking, go to sleep.
In the morning, leave the cell and follow the guard. After you reach the other floor, use Eagle Vision and note the man with the yellow glow. Speak to him.
After a short puzzle, rob the marked prisoner and return to sleep to your cell.
Unfortunately the key won't work. Speak with the Mason and you will receive a task of starting a brawl.
For that, approach the marked men and attack them. To win, you need to initiate slow motion with the counterattack button, knock enemies out of balance with the jump button and attack afterwards.
Optional objective: Limit prison guard deaths - 2.
After ending up locked in a cell, steal the key from the guard by the grates and head outside.
Now you will have to slowly follow the guard and quickly run upstairs as he turns left.
Optional objective: Reach Hickey within the given time - 2:00.
Optional objective: Completed all the constraints in one playthrough.
After speaking with your associate, quickly approach the room in front of you. As only the guard passes by, turn right and run up the stairs to the very top.
There you will be noticed by another enemy. Hide in the nearby cell and kill him when he approaches.
Now you have to quickly run to the marked goal and press the interaction button. If you're fast enough, the mission will end without the guard ever noticing what happened.