Season 2, Episode 1: "Be Right Back"
"Be Right Back" artfully explores artificial intelligence through the lens of grief, enlisting Domhnall Gleeson and Hayley Atwell to execute its melancholy story. In the episode, a man named Ash dies in a car accident shortly after moving to the country with his wife Martha. Grief-stricken, Martha hesitantly tries a new technology that creates a virtual version of Ash by sourcing his texts, videos, and social media posts. (Side note: you'll find an Easter egg of its origins in Bandersnatch.) After ordering a physical replica of Ash, she questions the authenticity of the technology as she realises that it lacks her husband's humanity.
The storyline is both poignant and unsettling, posing to viewers the metaphysical question, "What makes us human?" "Be Right Back," unlike many darker Black Mirror episodes, ends with a bit of a twisted uplift as we glimpse into Martha's future relationship with her daughter.