Deacon's Dark Past
Deacon's laid-back charm hides a genuinely dark past. He used to run with a synth-hating gang called the University Point Deathclaws, until the group killed a synth who turned out to be a real human. Disgusted, Deacon walked away, settled down and got married, only for his old gang to track him down and kill his wife, revealing in the process that she'd been a synth the whole time. It's why he ended up working for the Railroad.
