Prisoners of War

Prisoners of War is a side quest in the Fallout: New Vegas add-on, Honest Hearts.

This optional quest is received simultaneously with Flight from Zion along with Retake the Bridge and Sanctity of the Dead.

Detailed walkthrough
First, make your way up to Ranger Substation Osprey. You will encounter four White Legs guarding the prisoners. If you're a high enough level, one or more of them may be armed with anti-materiel rifles and/or brush guns.

After defeating them all, (as there is no peaceful solution) you need to open the cell to free the three prisoners. To do this you can either lockpick the Hard locked cell door or find the key in a toolbox upstairs in the Ranger substation tower. Either solution gives the same amount of quest XP, excluding for the bonus XP for successfully picking the lock.