So there's this super tall oak tree about a half a mile from the house—Sylvia has always imagined that "whoever climbed to the top of it could see the ocean" (2.1). So, you know, whoever climbs it could certainly see the heron.
Sylvia doesn't sleep at all and heads to the tree while it's still dark out. She starts by climbing a smaller tree and slowly making her way from one trunk to the other.
Although the climb is tough, Sylvia is somehow energized by the time she reaches the top.
She looks around and sees the heron below her, having "perched on a pine bough not far from" (2.8) her. She stays completely still and admires it.
The heron is scared away by a flock of cat-birds (not quite what it sounds like) and Sylvia slowly climbs down the tree, thinking about what the young man will say when she leads him to the heron.
Back at the house, Mrs. Tilley has discovered that Sylvia is missing and is out front calling her name. The young man—who had already guessed that Sylvia knew where the heron was—is outside, too.
But Sylvia surprises even herself when she can't speak and "tell the heron's secret" (2.13).
The young man leaves disappointed. No matter how much time passes, Sylvia is never able to fully convince herself that she made the right decision.