In which I describe a dream in which I describe an animated Batman movie. I've had fever and flu for a week now, and the dreams can be quite trippy.
Snow on the ground outside, a big house full of people. I needed to be alone for a minute, so I found a room upstairs. There was a small screen device on the desk. I pressed play and pointed it up and it projected all over the walls and ceiling, very immersive.
After watching for a while, I left the room and a friend asked what I had been doing. I felt guilty for being antisocial, but started talking about the plot of the movie, which involved nuking a city in a parallel universe. Apparently "karma" from that act didn't follow the character back to their own universe.
If karma has basis in physical reality, I would think that it would have to be a property of the higher-level multiverse, so such an act would follow you back. (In terms of programming, a higher-level closure.) The closest that I've come to multidimensional travel is dreaming. Feelings (and karma?) do follow me back from those worlds. Lucid dreaming has been a valuable method of self-analysis, literally walking through my own mind and patterns.