Lord of the Rings writer Philippa Boyens on changing the ending of Mortal Engines

From the moment the first traction city rolls onto the screen in Mortal Engines, it’s obvious that the world of the film is unlike any we’ve ever seen before — or even read. There are some surprises in store even for audiences familiar with Philip Reeve’s books, upon which the film is based, as director Christian Rivers and writers Philippa Boyens, Peter Jackson and Fran Walsh have managed to cram a breathtakingly giant world into the space of two hours while leaving room for potential sequels.

The first thing that stands out is how quickly the film gets going, relying more on context clues than exposition as it introduces viewers to the post-apocalyptic world. The reason is at the core of why the team wanted to make the movie in the first place.

“[Christian] literally wanted the momentum with which that giant city is rolling across the landscape to be echoed in the pace of the film,” Boyens explains. Indeed, the pace of the film is breakneck, and if that speed (not to mention the car chases) is reminiscent of Mad Max: Fury Road, that’s not by accident.

Rivers cites the film when speaking to Polygon about his inspirations, not in terms of aesthetic, but with regards to figuring out how to pace the action. “George Miller proved that you can just grab the audience and throw them into your world and say, ‘Keep up! I’m not going to overexplain this to you,’” Rivers says. “We’re guilty of a few things we have to explain, but for the majority of the world in the film, it’s like, ‘No, just come with us, keep up. Here are these characters, and learn about them as you go, learn about the world as you go.’”

There are more practical reasons for that sense of speed, too. “You cannot put everything that’s in that book into 120 minutes of screen time,” Boyens says. “You know you’re going to have to make some hard choices.”

[Ed. note: The rest of this story contains bigger spoilers for Mortal Engines.]

Universal Pictures

One of those choices was keeping the character of Katherine Valentine (Leila George), Thaddeus Valentine’s (Hugo Weaving) daughter, whose carefree worldview is shattered by the realization of her father’s ambitions, alive. At the end of Reeve’s book, Katherine dies, but in the film, she survives to witness the meeting of the Londoners and the Anti-Tractionists.

“She’s such a huge part — and almost, in a way, a bigger part than Hester — in the book,” Boyens explains. “We had to choose whose story we were telling. It’s not that we wanted to lessen the role of Katherine, but we felt that if we were going to tell it properly — and not just Katherine, but Bevis [Ronan Raftery], who’s also much bigger in the book than he is in the film — we couldn’t do it in one film. There were elements of their story that we can tell, but we’re going to tell them over two films [...] There is stuff in there that we did consciously put in there, like Anna Fang’s Windflower speech, is very much to set up what comes next.”

The question that follows, then, is whether or not a Mortal Engines sequel will happen to allow for those stories to bear full fruit. As both Boyens and Rivers note, the film is a gamble: the two main leads (Hera Hilmar and Robert Sheehan) are relative unknowns, Rivers is a first-time director, it’s not a reboot or a remake, it’s not American-centric, and it’s not adapted from a series with the same scale of built-in audience as, say, Harry Potter.

But, on the other side of the coin, Rivers says, “It’s quite simple to surmise that this film wouldn’t have been made if it was a standalone book.” Though whether or not the series continues will depend on how the film is received, the plans are definitely in place to get Mortal Engines 2 rolling along like the traction cities in it.