Reports of strange lights and a missing UFO investigator bring the team to look for aliens in a small town.
Tropes:
- Arbitrary Skepticism: Jenkins has a heavily lampshaded dose of this.Jenkins: No one beamed her anywhere.
Ezekiel: Says the guy with the teleporting door.
Jenkins: UFOs do not exist.
Ezekiel: Says the guy with the teleporting door. - Blatant Lies: Ezekiel tries to convince Mabel that "Colonel Baird" is Australian slang for "optical illusion." She doesn't buy it.
- Body Surf: The only way the extradimensionally-trapped townspeople can interact with normal reality is by temporarily possessing other people. They try to only do it for a few hours at a time.
- Double-Meaning Title: "City of Lights" refers to both the town of Wardenclyffe/Collins Falls with its gaslamps and mysterious glows, and Jacob and Mabel's shared dream of traveling to places like Paris.
- Downer Ending:Eve: Sometimes you just lose. You did good, all of you, but sometimes... you just lose.
- Fling a Light into the Future: At Jenkins urging, Eve makes a note in the Library's appointment book to check up on Collins Falls in a hundred years, in the hope that a future Librarian might be able to help them.
- Heroic Sacrifice: Mabel gives her life to allow Jacob to reach the capacitor's off switch.
- Hiroshima as a Unit of Measure: Cassandra compares the amount of energy that would be released in the explosion to the Tunguska event.
- Historical Domain Character: Nikola Tesla doesn't actually appear in the episode, but he features heavily in its backstory.
- The Needs of the Many: Cassandra convinces the Librarians that trying to save the 87 trapped people is too dangerous if it means risking an explosion that could kill ten times as many. Mabel accepts this; Norman and at least some of the others do not.
- Really 700 Years Old: Mabel has been frozen at her current age since 1915. Too bad it also keeps her stuck in town.
