This handsome young Engineer starts off just wanting to do good. He allies himself with Katherine because he thinks she might be able to help him correct the horrible living conditions workers in the Gut experience. After that, he gets involved in Katherine's quest to stop MEDUSA.
Soon, Bevis and Katherine find love. Then Bevis dies. Bummer. Sad ending for a boy with a terrible name.
Bevis shows us the strange life of an Engineer. Engineers are not only required to keep their heads shaved, they're also forbidden to feel physical contact with or attraction for anyone. Once Bevis meets Katherine, though, Bevis wants to know what love is. He wants Katherine to show him. "He watched her with shining eyes, filled with a feeling that he couldn't even name; something that they had never taught him about in the Learning Labs. It made him shiver all over" (25.52). The Engineers don't teach love. That's something you have to learn on the job, it seems.
Without even trying, Bevis and Katherine fall in love. She's attracted to his kind nature, and even to his awkwardness. "[Katherine] liked the fact that he was her secret. She liked his soft voice, and the strange laugh that always sounded as if he were trying it on for size, as if he had never had much call for laughter down in the Deep Gut" (27.2).
It's upsetting when Bevis meets a horrible end. When Tom, who also loved Katherine, blows up Valentine's airship, a flaming hunk of it squashes the flaming hunk Bevis into a flaming pile of death. Mortal Engines isn't a pretty book. Even someone who tries so hard to do good and be loved can meet a horrible ending. Life isn't fair.