Androcles' Lion: At the beginning of Episode 10, after Grace admits her flaws and is free of her memory tape, she helps fix the denizens of the Origami Car that Simon stepped on and crumples. At the climax of episode 10, those same origami denizens are the reason Grace survives the season; Simon kicks Grace off the train to be wheeled, but Grace survives because the origami birds grab her and fly her back up to the train.

Anyone Can Die: And how. By the end of the season, two of the book's four poster characters are dead. Tuba is murdered halfway through, while Simon perishes in the final episode. Grace and Hazel don't die, but the former is victim to two murder attempts, while the latter's innocence is buried six feet under.

Bait-and-Switch: The goal of Grace and Simon is to follow the cluster of numbers that will lead them back to the Apex. It turns out what Simon was detecting wasn't the Apex, but Amelia because of her humongous number.

Bait the Dog: The Book serves to flesh out and humanize the Apex more. Simon, in particular, has a number of sympathetic moments showing how he cares for Grace and the audience learns that he's been trapped on the train since he was 10. In "The Color Clock Car", he finally starts to warm up to Tuba, sharing a laugh with her and helping her through the car. The episode ends with Simon killing her by throwing her under the wheels of the train, gloating about it to Grace and Hazel, and it's all downhill for the remainder of the season.

Big Sister Instinct: Grace develops this for Hazel as the season continues. When Hazel decides to leave her and Simon in the penultimate episode to go with Amelia, Grace is completely devastated to lose her.

Bittersweet Ending: On the positive side of things, the Apex has been more-or-less disbanded. Grace and the children are now working to figure out how to move forward and help each other get off the train, and Grace herself now has a denizen partner in an origami bird. However, getting to that point forced Grace to deal with the death of a sapient denizen she was slowly growing attached to, being mercilessly rejected by a child she had grown to earnestly care for as an adoptive sister and will now never see again, almost getting killed by her best friend, and then watching said best friend die himself by literally crumbling into dust. No wonder the final shot is Grace giving everyone a melancholic smile.

Breaking Old Trends: Book 3 has several changes to the formula established by the first two: It's the first season to not have a Power Trio of main characters consisting of one human who needs to escape the train and two denizens who help them do so, instead being a Four-Temperament Ensemble. In addition, while said trios were very close True Companions by the end of their adventures, this is decidedly not the case for this season's main characters.

It's also the first season not to have a character zero out their number and escape the train at the end .

Brick Joke: In "The Mall Car", Grace tells Jesse to be careful where he aims the harpoon or he'll "end up like Lucy". Sure enough in "The Musical Car", one of the Apex girls, named Lucy, has an eye patch.

Call-Back: Jesse's name can be seen in "The Musical Car", as the composer of an opera entitled "Empathy Goes", with the song they perform ("When I Look at You, I See Me") being one he referenced in Book 2's "The Family Tree Car".

The Apex have the Unfinished Car from Book 1 as the second one that they raid in the first episode. There are also corgis there, additionally calling back to how Atticus befriended King Aloysius and promised to send aid to rebuild following the events of that episode.

The Jungle Car where Grace and Simon meet Hazel and Tuba is the same one depicted in the Book 1 poster.

In "Le Chat Chalet Car", The Cat is still angry at Grace's actions over what happened in "The Lucky Cat Car".

The Canyon of the Golden Winged Snakes Car in the seventh episode is the same one that MT visits during her travel montage at the beginning of Book 2.

The Cat gives Simon a tube filled with the memory extraction robots first seen in "The Tape Car".

Amelia's reign as the Conductor is why cars are being ejected, as One-One is having any car she made quarantined.

Grace gets trapped in her own memory tape, just as Tulip did in Book 1. Grace has very similar experiences in said tape, such as distorted memories and the static almost consuming her.

Central Theme: Empathy. The book starts off with a musical number detailing the joys of understanding other people, and the rest of the season tackles Grace's and Simon's struggles to learn empathy for denizens of the train. By the end, Grace has learned this lesson, while Simon's Lack of Empathy for denizens only gets worse and quickly expands to Hazel and Grace, unable to understand why they're beginning to fear and distrust him following his murder of Tuba. "Le Chat Chalet Car" has him begging Grace to be emphatic towards his fears and trauma .

. Poor parental figures and caretakers. Grace alludes to her parents being inattentive, while Simon's parental figure on the train (The Cat) abandoned him to fend for himself. Hazel doesn't remember her parents, but we later learn that she is a failed clone of Alrick, with Amelia refusing to acknowledge her as a child, much less being anything akin to a daughter. More broadly, Grace and Simon are the only source of guidance for the children of the Apex, and act more as manipulative cult leaders than caretakers. The only healthy parent-child relationship shown during the season is Tuba as a surrogate mother towards Hazel.

More broadly, Grace and Simon are the only source of guidance for the children of the Apex, and act more as manipulative cult leaders than caretakers. The only healthy parent-child relationship shown during the season is Tuba as a surrogate mother towards Hazel. Coping with shifting worldviews. The Apex hold the idea that numbers are a symbol of power and that the train exists as a playground for their personal amusement. By the latter half of Book 3, Grace has started to realize that this perspective is childish and has terrible consequences, ultimately apologizing her actions and working to reform the Apex. Whereas Simon refuses to face the truth that they've been wrong and doubles-down on his behavior, which leads to his death.

The damage that lies can do. The lie that Grace told a young Simon in "The Origami Car" is what would kickstart the entire Apex project. Her lying about not knowing about Hazel being a denizen results in her relationship with both Hazel and Simon being ruined. Simon rejecting the truth and becoming consumed by the lie that he's always right ends up in his death.

Children Raise You: ZigZagged. Grace and Simon are much more inclined to manipulate children than actually become better for them, they start to soften and open up after spending extended time with Hazel. Only for Simon to continue indulging in his old behavior and become even worse, while Grace continually chooses to save face in front of Simon over outright protecting Hazel. The poor girl ultimately abandons the duo, realizing neither are capable of providing the care and protection she needs. Only after overcoming her problems on her own does Grace truly thrive as a caretaker.

Cult of Personality: As noted back in Book 2, the Apex is one formed around the previous Conductor, seeing One-One as a usurper. Instead of trying to reduce their numbers, they believe they must increase them by causing mischief on the various train cars. They also have a sound wave marked across the middle of their face, denoting the analogue hijacking noise she used to control the Steward. When Amelia finds about it, she laughs at how ridiculous it all is.

Darker and Edgier: Featuring two sociopaths as our protagonists, this is the darkest book so far. By the end of the season, all of the main quartet has suffered to some degree: Tuba and Simon are killed (one murdered by the other, the other graphically killed by a Ghom), Hazel has become thoroughly jaded and distrustful of the world , and Grace is a victim of attempted murder at the hands of her closest friend

Does This Remind You of Anything?: After Simon kills Tuba, he becomes much more aggressive, gets into Grace's personal bubble and is mad that she's "not the way she's supposed to be". Combined with Hazel wanting to be strong to protect her and Grace, he comes off as an abusive boyfriend/husband, not helping that Grace is keeping secrets from Simon out of fear.

In "The Origami Car", Simon uses the nanobots that The Cat gave him to send Grace into her own tape against her will. He inserts himself into her memories, intentionally uses some particularly painful ones to break her will, ignores all her objections, and then just leaves her to rot when he gets what he wanted. The whole scene carries some horrifying parallels to assault, especially when Grace later wakes up, visibly disgusted and shaken by the whole affair.

Dramatic Irony: The Apex raid the Unfinished Car in the first episode... the car made by the Conductor they just so happen to worship. In fact, everything Grace and Simon tells about the Conductor to Hazel in "The Debutante Ball Car" is just filled with this.

Family-Unfriendly Death: If you thought Mace's death was bad, this season is even worse! Simon's death is not pretty, as his skin graphically melts and his bones are turned to ash right in front of Grace and several of the kids.

Foreshadowing: Much of Hazel's seemingly random bits of trivia are direct references to Freeze Frame Bonuses from Book 1's "The Past Car"

For Want of a Nail: A younger Grace in "The Origami Car" lied about how the numbers worked instead of admitting that she herself had no idea, eventually leading to the ideology of the Apex years later.

Getting Crap Past the Radar: The intimacy between The Cat and Frank, given how Frank first appears with his robe open and making it look like he was naked. Word of God confirms that they are in a relationship, though notes The Cat would claim it's just casual.

Given Name Reveal: "The Canyon of the Golden Winged Snakes Car" has Simon call The Cat Samantha .

Gory Discretion Shot: Unlike the death of Mace in the previous season, the death of Tuba is not seen, instead having lightning crash to depict it.

in the previous season, is not seen, instead having lightning crash to depict it. Averted with Simon's gruesome death at the hands of a Ghom.

Internal Reveal: While the audience is already well aware of how the train functions and what the numbers actually mean by this point, Grace and Simon don't learn the truth until Amelia explains everything in "The Hey Ho Whoa Car."

Karmic Death: Simon. He meets his end with the same thing that brought him into the Apex, a Ghom. Ironically, Grace saved him from another karmic death via wheeling.

Know-Nothing Know-It-All: The Apex are convinced that higher numbers are better and equal power, despite it not being possible for that to be further than the truth. "The Origami Car" reveals that this started when Grace met Simon and acted like she got it that high intentionally rather than admit to being clueless.

Late-Arrival Spoiler: Mentioning anything about Amelia's role in this season spoils the end of Book 1.

The Little Detecto: Simon has a device that can track passengers by their numbers. Amelia's is so large that he mistook her for the entire Apex.

Amelia has a scanner that can detect anomalies, things that she created during her time as the Conductor.

Meta Twist: The Wham Episode of the last two books, each featuring some sort of death scene ( Atticus and Mace , respectively) the death scene happens in Episode 5, though Episode 8 is still a "Wham Episode" in its own right . Instead of one major death, we get two: Tuba and Simon.

. While Grace makes significant progress on this front, none of the passengers seen this season manage to get their numbers down to the point of leaving the train.

Protagonist Journey to Villain: Downplayed with Simon, who was already a sociopathic Villain Protagonist from the start, but like Grace, has some redeeming qualities and sympathetic traits shown during the first half of the season. Then he murders Tuba, and the second half sees him losing any such good qualities and becoming worse and worse, until he eventually takes up the mantle as the Big Bad of the season and tries to kill Grace, who was once his best friend.

"Ray of Hope" Ending: While Simon is dead, Grace decided to reform the Apex. Instead of staying on the train, they decide to help each other get home. After the credits, we see Grace's number rapidly decreasing.

"The Reason You Suck" Speech: The beginning of Episode 10 contains one for Grace, as she's confronted by a nightmare-version of Hazel yelling at Grace for her manipulative and cowardly behavior. The nightmare Hazel even accuses Grace of killing Tuba, to which Grace responds by pointing out that it was Simon who killed Tuba. Hazel retorts that while that's true, "He didn't come up with the idea to wheel denizens on his own!"

The climax of Episode 10 contains one for Simon, as Grace tells him that while he's in a lot of pain and Grace can see that, Grace is not responsible for all his problems.

Redemption Quest: For Grace , as they progressively undergo Character Development and become a better person over the course of the season, making a HeelFace Turn by the end.

Reformed, but Not Tamed: Amelia is trying to be a better person, but 30+ years of limited social interaction has not helped things, and she has a card by One-One to remind her that the passengers matter.

Ship Tease: It's very heavily implied in the first few episodes of Book 3 that Simon has a thing for Grace due to him frequently blushing or smiling when she shows him affection. Grace for her part doesn't seem to be in love with Simon, but she clearly cares for him deeply, while also being comfortable enough to casually touch him or play with his hair several times. The two are also paired together as dance partners in The Debutante Car and seem to have fun, particularly Simon, in spite of being the most opposed to it initially.

When Grace apologizes in "Le Chat Chalet Car" for ignoring how troubled Simon was, she reveals that her number has been going down, getting uncharacteristically vulnerable. When he assures her that he'll always be with her, she embraces him tightly.

Simon's feelings for Grace take a dark turn in the second half of the book, where he starts acting like an abusive boyfriend to her. By the end of the season, any feelings he once had for her have been completely destroyed.

Shoo Out the Clowns: Hazel leaving with Amelia at the start of Episode 9 is when things start getting darker fast, not that they weren't dark enough already by that point.

Villain Protagonist: The two main characters of the season, Grace and Simon, are members of the hedonistic Apex, which is sadistic and cruel to the train's denizens. Over the course of the Book, Grace gets better and performs a HeelFace Turn by the end, while Simon gets even worse and becomes the Big Bad

We Used to Be Friends: Simon and The Cat were close when the former first came to the train, as she was his denizen companion. But after she accidentally abandoned him when they were running from a Ghom and never came back to save him, he became extremely bitter and grew to resent not just her, but all the train's denizens.

By the end of the season, Grace and Simon — best friends, with the latter clearly having a crush on the former — have become this. He leaves her trapped in her own memories, takes over the Apex, and tries to murder her when she returns, even after she saves his life .

Wham Episode: "The Color Clock Car" ends with Simon killing Tuba , as well as the reveal that Hazel isn't human .

, as well as . "The Hey Ho Whoa Car" reveals that Hazel is one of Amelia's failed attempts to recreate Alrick, and that any car with her in it will be ejected if/when the scanning pulse hits it. Simon also views a tape of Grace's memories and finds out that she purposefully didn't tell him about Hazel's inhuman status.