Bill is a British biologist who researches triffids, a mysterious plant species. Before the story begins, he is temporarily blinded by a triffid sting. This causes him to miss a catastrophic event wherein everyone who watched a passing comet was permanently blinded. Early on, he saves Josella, another sighted person, and together they navigate post-apocalyptic England.

Throughout the novel, Bill must make sense of a world without order by adjusting his morality and ethics accordingly. His primary struggle is choosing between self-preservation and altruism. Initially, he thinks it is better that he has no loved ones to look after or worry about. As he falls in love with Josella, however, his views change. He warms not only to the idea of altruism but the concept of mandatory procreation to rebuild society. 

When he and Josella are separated, he spends most of the novel searching for her. His character arc shows Bill change from a proud loner to a man desperate for family. He finds what he is looking for in a young, newly orphaned Susan, as well as his beloved Josella once they are reunited. 

Bill becomes focused on ensuring their survival, especially once he and Josella have children of their own, completing his transformation from selfish to selfless.