And then Miles caught a fish. There it flopped, in the bottom of the boat, its jaw working, its gills fanning rapidly. Winnie drew up her knees and stared at it. It was beautiful, and horrible too, with gleaming, rainbow-colored scales, and an eye like a marble beginning to dim even as she watched it. The hook was caught in its upper lip, and suddenly Winnie wanted to weep. "Put it back, Miles," she said, her voice dry and harsh. "Put it back right away." (17.33)
This lucky fish was supposed to be breakfast, but Winnie's struggles with the concept of death allow it to live another day. You see, while they've been fishing, Miles and Winnie have been talking a lot about life and death: what it means to live forever and what it means to have to die. Amidst all this chatter, Winnie comes across a mini-version of her own choice—live or die? And she chooses life.
You might think, based on this scene, that Winnie will end up drinking from the spring and joining the Tucks in eternal life. Why do you think she changes her mind?