Thanks so much! Script supervisors are definitely a crucial role and I will look into getting some on the show.
A "story beat" is basically the minimal unit of forward motion in a story. So, in this case, the first major story beat would be Sam and Al realizing they've switched places, the second would be Sam realizing he's stuck in the imaging chamber, and the third beat would be Sam figuring out how to get out of the imaging chamber.
Thanks!