A Short Drink from a Certain Fountain - S5-E11
Continuity mistake: When Raymond arrives to check on Harmon, Flora is sitting at the breakfast bar opening the morning paper. She's holding it straight up in front of her, but when the shot reverses angles, the paper is suddenly lying flat on the bar. (00:16:15)
Answer: It's explained in the episode. The aliens are experimenting to see how humans react to various scenarios. This just happens to involve them using super strength.
Thanks. It's been a long time since I saw the episode so I forgot.