The poem begins in a dingy prison cell, with the late-afternoon light slanting down through the wooden bars. The speaker clinks his English tea-cup against the bars, whistling a tune with downcast eyes and…hey! those aren't prison bars. Those are trees! Lime trees, to be exact. And this is no prison but a lovely English garden. We'll have to be careful with this here speaker.
Our imagination busts out of the prison and takes on a walk along the heath, which is filled with delicate flowers and small shrubs. We're running to catch up with the speaker's friends – man, they are walking fast, as if they're on a mission. ("We can't miss the sunset!" they mutter under their breaths). They pass into a dark ravine, where they must crawl over legs and brush away mossy branches from their faces. They pass over a stream on a log, and a roaring waterfall sprays the vegetation with a heavy mist.
They walk back up the ravine and, all of a sudden, the sky opens up and they are standing on the heath again, looking out toward the ocean. They finally stop so that we can catch up with them. We regain our breath just long enough to see the blazing sun set on the horizon, lighting up everything in the landscape.
Back in the bower, the speaker notices the beauty of his own surroundings, on a smaller scale. The effect of the light on the plants in the garden resembles the effect of the light on the plants in the ravine. The prison bars turn back into trees and the dingy floor of the cell becomes a rich soil that grows flowers and ivy. Birds and bats flutter overhead. The day's last rook forms an imaginary line between the speaker and his friend Charles.