Kinda relevant but:

Started a new job a month ago, one of the guys who works there really piqued my interest. He seemed a bit "off". He'd never look at me in the eyes when he spoke, he was constantly darting his eyes around and it just felt weird. I assumed he had Borderline Personality Disorder from our brief encounters.

Had our Christmas party yesterday and I made it my mission to talk to him and get him to open up. I knew he had a fascination around a certain topic so I used it as as in. After he was relatively comfortable, I asked more broad questions. He opened up and mentioned he has a vast history of mental disorders. Didn't want to ask if it was BPD in case he jumped at me and tried to kill me. We spoke for a good 45 minutes.

He seems cool, I'd like to become better friends with him. He just seems very interesting, people that are "unstable" genuinely do fascinate me.