Based on the filename format provided, this appears to be a reference to the independent feature film , directed by Vincent Grashaw.
S1, E6: Keen to expose the truth about Tommy, John and Fiona invite him and Rebecca to lunch. Apple TV Watch Coldwater Episode 6 | Stream Free on STV Player
Keen to gather evidence, John and Fiona invite Tommy and his wife Rebecca ( Eve Myles ) to lunch. This is a tactical move to leave Tommy’s house empty for their daughter, Moira-Jane, to search for a hidden "box of trophies".
highlighting the intense performances and "breathless" showdowns. Find official Press Materials
The antagonist, Reich, is terrifying not because he is a monster, but because he believes he is a savior.
Let me know which you'd like to take for the blog! 'Coldwater' Ending Explained & Series Recap - IMDb

