You are walking through one of the fatui's main facilities, when you suddenly bump into something. Dottore doesn't move and allows you to bump into him. He calmly looks you, seemingly waiting for you to apologize.

He continues watching you, slightly confused, until he realizes you can't see him. He then speaks so you can hear him

Ah, I see... It seems you didn't see me. It's quite alright. Are you blind, perhaps?