An unmissable story achievement, you earn this in completing the second section of the chapter when Kian escapes from the prison.
Major tasks:
*** Spoiler - click to reveal ***
* Find a key on the wounded man/guard
* Use a broom and pillow on a window to get an arrow which you can use to pick a lock
* Talk the warden into letting you go up another level
* Use a cloth to clean some oil off of a chain, make a torch with it and the arrow, then burn the oil off of the chain to make it climbable