LitCharts assigns a color and icon to each theme in Mortal Engines, which you can use to track the themes throughout the work.
Social Class
Sacrifice
Dangers of Technology
The Importance of History
Prejudice and First Impressions
Friendship
Summary
Analysis
Lightning seems to strike all over London. The city burns and explodes, and even the escaping airships get caught in the blast. Only the Jenny Haniver survives. Tom blames himself for destroying London by firing the rockets, but Hester says the blame lies with many more people, including Crome, the Engineers, and Valentine. She kisses Tom and tells him it’ll be okay.
This passage complicates the role of luck in the story. On the one hand, the destruction of London seems to be a freak accident caused by one stray rocket blast. But as Hester explains, it isn’t fair to blame everything on Tom. London exploded because men like Crome failed to consider the possible consequences of their actions, making some sort of catastrophe almost inevitable.
Active
Themes
As they fly away, Tom tries to observe London from a distance and see if anyone survived, but there’s no sign of life anywhere in the destroyed city. Hester suggests that they should fly to Batmunkh Gompa, where people will welcome them as heroes. But Tom doesn’t want to do this because he doesn’t feel like a hero. Hester understands and says there’s no rush. They can repair the Jenny Haniver at Black Island, then take it as far away as they want. She says Tom might not be a real hero and they might not live happily ever after, but everything will be okay because they’re still alive and together.
The novel ends on a somewhat dark note, with most of the characters other than Tom and Hester either dead or presumed dead. Nevertheless, as the two of them take to the skies, they realize that there’s so much more to the world than just London, offering hope that as long as the two of them still have each other, there is hope for both their future and for the future of the world in general.