This episode is based off of Francis Ford Coppola's Apocalypse Now (1979)
During the opening scenes at the police station, Missy is shown being fingerprinted. The page has five spaces despite the characters all only having four fingers. She places her third (index) fingerprint onto the fourth space, leaving the third space blank.
Not only does the episode reference Apocalypse Now but the book it was based on, The Heart of Darkness, with the characters literally entering a giant dark heart.