I recently watched Lake Henry. It's quickly become one of my top three episodes in the entire Black Mirror series.
Spoiler Alert! Continue reading at your own discretion.
Let's dive into an analysis.
When Pia is viewing the crime evidence video, she hears from her mother-in-law, "The pie is ready." As she turns around, the door is already open, and her mother-in-law is in the room.
In reality, there would be a moment between hearing the voice and the door opening. This would give Pia time to shut her PC. Thus, the mother-in-law hasn't seen the evidence video. However, for the sake of suspense and to give the audience a feeling of "Did she just get caught?", the scene of the door opening has been intentionally omitted, emphasizing the eeriness.
Another striking scene was how meticulously the murderer arranges the potato muffin. The sheer care of a killer setting something up is spine-chilling. Moreover, Pia is then obliged to eat this pie.
The direction where the aunt, before her suicide, puts on a mask seen through the mirror, shielding it with her elbow first, is exceptional. Without any camera movement or cuts, we witness the transformation.
This drama has some parallels with the theme of "Mother's Proof" - about a mother willing to go any lengths to save her beloved son.
In the scene where Pia escapes from home and her aunt chases her, it's refreshing to see the latter wielding only a light and not a weapon. Typically, a chasing murderer has a weapon in hand (which is terrifying in its own right). Perhaps the aunt just wanted a conversation with her beloved nephew's lover without causing harm.
Finally, the Oscar mask suggests a provocative message: Is the film industry, much like the murderer, enjoying homicide? The parallelisms seem to indicate:
This leads to the unsettling message: Even the audience, in a way, shares the same morbid curiosity as the killer.
Mask worn by the murderer:
Film award trophy mask: