The Lateness of the Hour - S2-E8
Visible crew/equipment: As Robert is pouring Dr. Loren's drink, an equipment shadow moves across the top of Jana's head in the foreground. (00:08:20)
The Lateness of the Hour - S2-E8
Visible crew/equipment: When Jana is screaming "No pain!" at the top of the stairs, a film crew member's shadow can be seen moving on the wall behind her. (00:22:30)
The Lateness of the Hour - S2-E8
Visible crew/equipment: The boom shadow intrudes briefly at the upper left of the shot as Jana stands at the window and says, "Rest in peace." (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.