Free the prisoners | Controls MGS V: Ground Zeroes Guide
Last update: 11 May 2016
The convict
If you choose to rescue the convict first, go back to the refugee camp (the tents near the starting point). He is lying next to a trunk and the toilets, surrounded by three guards. Get rid of these guards or knock them out to rescue the prisoner unnoticed.
If you don't want to kill the enemies, You can distract them by throwing a magazine towards the tents and then go to the prisoner.
Extract him in a helicopter. You can call it to the place where you've started the mission - this is the quickest way. Rescuing the prisoner is rewarded with the achievement "Rescue" and with the cassette Chico's Tape 4.
The rest of the prisoners
The rest can be rescued in any moment, before completing the mission. You just have to open the cells and escort them to a landing zone. In most of the missions, there is a possibility to rescue prisoners, which is rewarded with a high score and makes it possible to obtain the S rank.