This episode centers on a scientist extracting the pheromones of his victims, all male spouses, and using the resulting substances as a perfume to get close to their wives. While the Fringe team investigates, Peter learns more about the Observer September.
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This episode's glyphs spell:
These glyphs foreshadow the return of the porcupine man from S1E13 - The Transformation in the next episode.
The Observer is featured in the episode and interacts with Peter.
A door marked "Burn Unit" in 'The End of All Things' hints at the villain's burned face and burned marks on his victims' necks in 'A Short Story About Love'.
The porcupine on the calendar in September's apartment in 'A Short Story About Love' foreshadows the return of the Porcupine Man in 'Nothing as it Seems'.
The Greek phrase "Na einai kalytero anthropo apo ton patera tou" that Olivia uttered in "A New Day in the Old Town", which was something Elizabeth used to say to Peter, translates to "Be a better man than your father."
The Beacon helps Observers find our world. The Beacon's appearance in "The Arrival" may have been a test or preparation for the future Observer invasion as seen in "Letters of Transit".
Olivia gave Nina a hug and a kiss in "Five-Twenty-Ten", suggesting that they reformed a personal relationship.