In chapter nine there are 7 Hostages that you have to save

Make sure you hogtie each guard before saving any of the hostages. After you have saved them you will reach a part where you will go up against a heavy machine gunner. Shoot the support beams to block the windows so the hostages dont get shot and killed. You can restart from any chapter if you think you missed any hostages or if you think any have been killed. You will be told when there are hostages in the area. You will get this trophy/achievement once you finish talking to the hostages, destroyed the support beams and get back into another gun fight