In chapter 10 of The Mouse and the Motorcycle, author Beverly Cleary describes many symptoms that show Keith is very ill, symptoms that Ralph, the mouse, is the first to notice.

Ralph begins to suspect something is wrong with Keith when, after Keith returns to the hotel room to get ready for dinner, Keith washes his face, then sits back down on the bed and "stare[s] at the wall." Keith doesn't play with any of his toys or eat anything. When Ralph asks what's wrong, Keith says, "I feel sort of awful." Keith leaves for dinner but returns very early, having been unable to eat anything but soup and crackers, and goes straight to bed. When Keith's parents come into his room after dinner, they only note that he has a slight fever. But, soon after Keith falls asleep in bed, Ralph hears Keith moving around restlessly and mumbling. Keith's mother hears Keith too and returns to check his temperature, seeing that he's now "burning up." Keith's movements and mumbling are a sign that his fever is very high.

The climax of the story begins to develop the moment Keith's parents are unable to find any aspirin to give Keith. His father goes down to the hotel desk to see if he can get an aspirin, but the night clerk is unable to find any. The nearest pharmacy is 25 miles away and had already closed for the night. The doctor is telephoned, but he is busy tending to victims of a car accident and cannot come to the hotel. All the Gridley family can do is wait until the morning and hope the milkman can bring aspirin when he comes. Ralph, understanding the danger of the situation, decides he should go out and search among the hotel rooms to find and bring an aspirin.