Apple and the Aspirin Tablet — Gerald Duff

In The Apple and the Aspirin Tablet (a selection from the short story collection Fire Ants and Other Stories by Gerald Duff), war is raging worldwide, and a young boy entices his sister into biting into an apple in which he's concealed an aspirin. The babysitter, a busybody aunt of the two, concludes the child has swallowed poison, put into the fruit by German prisoners of war in Southeast Texas. Many years later, the old man the boy's become realizes why he couldn't tell the truth about the aspirin he'd put in the apple for his sister to eat.