Mafia III

This mission will become available after completing the second to last main story mission entitled "Ain't Nowhere Safer."

Once you regain control of Lincoln after a long cutscene in Roxy's bedroom, head over to The Voice and speak with him about the fall of Slim. He will inform you about troubles in town now that Slim is locked up. This will, in turn, unlock three side missions around town: "A Good Man," "An Instrument of Justice," and "The Proverbial Canary."

Complete the aforementioned missions, return to The Voice, and the achievement will unlock.