I remember when we got our first dog. My now-wife left us alone in the pet store for a few minutes where they had held the adoption event, and I remember our new dog looking back at me with questioning eyes from the end of the leash, worried, not understanding what was happening and trying to find some reassurance from these unfamiliar humans.
I was terrified of being alone with her. I didn't know what I was doing being totally responsible for an animal, and it clearly made an impression. I saw her reaction change immediately from "Is everything going to be alright?" to "We're going to die. We're definitely going to die!"