Sean O'Faolain's short story of childhood exploration and imagination begins as with a description of one of twelve-year-old Julia's favorite places, the Dark Walk. This overgrown path always fills Julia with a scary sense of delight as she runs from the warm sunshine through the dark damp tunnel of overgrowth. This particular year, she introduces her younger brother Stephen to the Dark Walk. Julia takes extra delight in her brother's excitement and joyful terror as they run back and forth on the path. When they get back to the house, the children share their experiences with the adults. As often happens with competitive siblings, they devolve into name-calling and arguing.
To put an end to the squabbling, one of the grown-ups asks, "Did you see the well?" At first, Julia expects this to be yet another made-up story that adults tell to kids. However, her curiosity gets the better of her, and she returns to the Dark Walk in search of the well. Sure enough, Julia finds a small well carved into the rock, hidden under ferns and fallen leaves. Incredibly, she finds a panting trout in the water. Julia rushes back and retrieves her brother. The trout is so interesting that the two children forget their fear of the place.
The presence of the fish amazes the adults as well. They are all at a loss to come up with a rational explanation of how it came to be trapped in the tiny well. They posit several theories, but nobody is too convinced. Julia goes back to the well to examine the trout further while Stephen stays behind to hear his mother's fantastical tall tale she makes up explaining how the fish came to its place on the Dark Walk.
Julia feels a great deal of sympathy for the trout. Its prison in the rock is so small that it doesn't even have room to turn around. Wondering what it must eat, she brings it food but the fish does not eat.
As the long summer days continue, Julia and Stephen's mother continues to tell them bedtime stories, involving moral lessons and fairy godmothers, to explain the presence of the trout. Stephen is fascinated by them, but Julia refuses to entertain such nonsense.
Unable to sleep, Julia slips out the window with an ewer and heads over to the trout. In a frantic moment of fright, Julia reaches into the watery hole, picks up the fish and puts it into the ewer. Julia runs down to the river and places the fish into the water. In a sense, she has become the trout's fairy godmother.
The next morning, Stephen comes to her announcing that the fish is gone. Instead of explaining what she did the previous night, Julia simply says that it must have been a fairy godmother.