With the quest for his father's fate over, Jean is now more determined than ever to honor the pledge he made to Nadia to help her travel to Africa and learn her personal history.
When Nadia visits the Engine Room, Jean repeats the broad strokes of Nemo's explanation about the Particle Annihilation Engine and what would happen with it in the wrong hands.
Easily Forgiven: Despite their earlier schism, Hanson quickly forgives Jean when the latter finally asks for help. He is justifiably a little smug, sure, but it's also not mean-spirited and is all in good humor.
He's Back!: The entire episode is basically Jean (with Nadia's help) pulling himself back from the Heroic BSOD and Despair Event Horizon he got hit with during the two previous episodes.
Internal Reveal: Minor example. Since Jean was the one who found King in the Engine Room in Episode 11, none of the other characters saw it or the Particle Annihilation Engine. By following Jean to try and give him a snack, Nadia finally gets to see the heart of the Nautilus (and is left just as baffled by Jean as what the hell a 'Particle Annihilation Engine' is supposed to be).
He's Not My Boyfriend: Nadia's angry denials to Marie when she and King slyly try to invoke the Trope.
Lethal Chef: Even after working in the ship's galley with Grandis for some time, Nadia still can't cook if her life depended upon it.
My Way or the Highway: It's revealed that Jean's inventions fail not because he's a bad inventor, but because he's sometimes staunchly against receiving feedback from people that can help him. He eventually realizes that this will get him nowhere and accepts Hanson's input.
You Are Not Alone: Ironically, despite trying to impart this lesson to Nadia throughout the series, Jean himself has to learn he's not alone either and that he has people he can ask for help instead of going at it alone.
