The Enterprise accidentally breaks into an alternate universe, one in which magic is real, and are immediately greeted as old friends by a satyr-like figure named "Lucien" who brings them down to his planet to show them the wonders of magic on his planet, Megas-Tu.
Then, some Puritans show up to put them on trial for past misdeeds and reveal that the jolly "Lucien" has another name that's more familiar to them.
This episode provides examples of:
- Beethoven Was an Alien Spy: The Megans traveled to Earth and taught medieval humans genuine magic. They left after the people of Salem wigged out and started murdering them.
- Fate Worse than Death: Lucien is sentenced to be alone in a separate universe for the rest of time. Kirk protests that this is as good as a death sentence.
- Getting Crap Past the Radar: The writer of the episode originally wanted to have the crew meet God. The execs put the kybosh on it, but said that meeting the Devil would be fine. This mirrored his previous experience writing for a police show, where he was not allowed to show a man in bed with his wife, only with a mistress. Asmodeus also calls Earth "hellish".
- Heart Is an Awesome Power: Spock deduces that belief shapes reality in this universe, therefore, the existence of magic is quite logical. He soon demonstrates it himself, and implores Kirk to "believe" during the showdown with Asmodeus.
- Humans Are the Real Monsters: Asmodeus calls humans the most vile, treacherous species in the universe.
- Humanity on Trial: The whole crew is put in pillories by Asmodeus, who still has bad memories over what happened in Salem.
- Louis Cypher: "Lucien" isn't trying to hide very hard to hide his true identity. It's just that Kirk isn't as up on his Abrahamanic lore as viewers are.
- Love Potion: Lucien points out a lady purchasing one of these. Since you can look as young and beautiful as you want, apparently these are the new necessity for getting a man.
- Paper-Thin Disguise: A horned satyr whose name means "Light" offering apples to the crew.
- Trickster Archetype: Lucien is mischievous and constantly laughs over Kirk's bafflement with the magic universe, but he's genuinely fond of humans.
- Satan: It's pretty clear from the start who "Lucien" really is. Especially when he hands a couple of apples to the crew on his tour of the magic universe.
- Satan is Good: This doesn't come with God Is Evil like it usually does, but Lucien really isn't a bad guy here. In fact, he's a lot nicer and more open-minded than the other people in his universe, who take a lot of convincing to believe that humans are okay now.
- Secret Test of Character: Asmodeus' cruel sentence on Lucien proves to be a test to see if humanity has truly changed. Kirk's willingness to fight for Lucien proves that they have, and Asmodeus declares that they're welcome to visit at will.
- Wizard Duel: Kirk takes on Asmodeus in a battle of magic to save Lucien from eternal isolation in a bubble universe. He's hopelessly outclassed, but fortunately Asmodeus is just testing him.