Bill Masen is a fictional character from the science fiction novel "The Day of the Triffids," written by John Wyndham. He is a biologist who becomes one of the few survivors in a post-apocalyptic world where most of humanity has been blinded by a comet shower. Bill's knowledge of plants and biology helps him navigate the dangers of this new environment. Throughout the story, Bill encounters the deadly Triffids, carnivorous plants that can move and attack humans. As he struggles to survive, he also seeks to find other survivors and rebuild society. His character represents resilience and adaptability in the face of overwhelming challenges.