To free Haken in Stay of Execution in the Hidden City in Shadow of the Tomb Raider talk to the musician in the square to lure away the guards.
All Hidden City Guides
All Shadow of the Tomb Raider Guides
Talk to the guy squatting to the left of the prison to get him to help you open the door.
Then talk to the guy standing to the right of the prison to help the other guy.
Walk up to the prison door and lead Haken out of his prison.
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