What is the main plot in the story "A White Heron"?
Sylvia is a nine-year-old girl who spends most of her life wandering the woods near her grandmother's home near the Maine coast. Her only friend is her grandmother's cow, Mistress Mooly, with whom she plays a game of hide-and-seek each night. One day, she encounters a man in the woods, who is lost after a day's hunting. He follows her home, and he spends the night. The man reveals that he is an ornithologist, collecting specimens for his collection; he is specifically looking for a rare white heron, one which Sylvia has seen in the woods. Together they go hunting for the heron the next day, but they do not spot the bird. Sylvia develops a crush on the young hunter, and she heads out early the next morning in hopes of spotting the heron. She climbs a tree and, sure enough, she discovers its nest. But when she returns home to join her new friend on another hunt, she fails to reveal the location of the nest and the bird about which she has dreamed.