This achievement is story line based.
*** Spoiler - click to reveal ***This quest requires you to sneak into Bargate Prison through the hidden back door that the archeologist revealed to you. After fighting your way through the pathways and underground tunnels you will enter Bargate Prison and be captured by Jack of Blades and imprisoned. To escape the prison you need to win the yearly race the second time and open one of the warden's journals. The key to escape will be inside. Once you are returned to your cell you can let yourself out and fight your way out of the prison. Your equipment is inside the guards sleeping quarters in the courtyard. Once you escape out the back entrance with your mother the quest completes and the achievement unlocks.