In the random encounter "Slavers Escort", three slaves are being escorted by slavers. The slaves will beg the Lone Wanderer to set them free if spoken to. Disabling their collars results in positive karma, providing the Wanderer is successful, however the slavers will turn hostile.
In the random encounter "Escaping Slaves", two to three slaves will attempt to escape from slavers. The Lone Wanderer cannot speak with the slaves if they manage to escape the slavers who will fire at them. Instead, the slave(s) will continue fleeing indefinitely.
If the random encounter "Looking for the Temple of the Union" occurs, three slaves on the run will ask the Lone Wanderer for the location of the Temple of the Union. They can be dismissed, helped, or lied to.
Three slaves can be freed from Evergreen Mills. If they are freed, they will stay at Evergreen Mills.
During Into The Pitt, a few slaves can be found at the train tunnel from which the Lone Wanderer has access The Pitt. Their clothes are required to continue in the quest.