Billy, who narrates the novel The Princess Bride, is a young man who does not enjoy reading and would much prefer more active pursuits like sports. His teachers try to get him interested in reading—they see his potential—but they cannot convince him that reading is a worthwhile activity. 

One day, he comes down with pneumonia and this causes him to be sidelined for a long time. He cannot participate in any activities, and he is too weak for anything but laying in bed. 

I was pounding the top of the radio to get it to work right and that was how they discovered I was delirious with pneumonia. Pneumonia today is not what it once was, especially when I had it. Ten days or so in the hospital and then home for a long recuperating period. I guess it was three weeks in bed, a month maybe. No energy, no games even. I was just this lump going through a strength-gathering time, period. 

In the book, Billy's father begins reading him the story in his broken English. In the movie version, it is his grandfather who reads the book to him. Billy's sickness is not specified in the movie. Additionally, he is playing video games when his grandfather arrives, which is different from the book.