Continuity mistake: When he introduces himself to Millicent inside the train station, Paul is wearing a dripping wet raincoat. It stays wet in the close-ups, but in the next several inter-cut two-shots, it's completely dry. (00:11:15)
Continuity mistake: As Millicent starts toward the women's restroom, the door handle is to her right. However, in the next shot showing her in the restroom with the door now behind her, the handle is now to her left. (00:20:00)
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.