Andy tells Darby that Bill had injected himself with morphine because the rooms monitor heart rates, and build Bill's spiked six minutes before someone entered the room. Morphine causes both lower heart rate and lower blood pressure because it is a central nervous system depressant.
Obvious green screen when Darby and Rohan are talking during their hike.
As with previous episodes, no matter how cold the temperature is portrayed to be outside, no one's breath is visible. Darby does wear a coat this time, indicating the outdoors is even colder than episode one (when she wore no coat in near-freezing temperatures).
At 14 minutes, a person's hand and shadow can be seen moving off screen, to the right, further up Darby's bed, though she is supposed to alone in the room. When she steps into the en suite, reflection of movement can be seen in the coffee maker.