This is obtained in the chapter "The pursuit". The second of Kurt's sequences is a dream-like scene where you walk through a road full of ghosts.
Just walk or run forward without colliding with the ghosts. If one of them turns into smoke, means that you have touched it and the achievement is voided. In that case, exit from the game and select "Continue" to start the dream sequence again.
As soon as the achievement unlocks, you can hit pause, Exit, and then continue from the menu for the opposite achievement.