It was a dark and stormy night… just kidding, Shmoopers. It's a dark and quiet night, and the speaker welcomes his friend and her sister to join him on a bridge overlooking a green bit of nature, where they begin chatting about the night sky.
A nightingale interrupts their chat with its melancholy song. But wait, says the speaker. Who decided that it sounds melancholy? Nature is never melancholy, he argues. It all just depends on the mood of the person who is listening.
In fact, he goes on to say, everyone would benefit from spending more time in nature, really experiencing it, rather than projecting their current feelings onto it. He then recounts a story about a pretty grove where a maiden makes nightly visits to listen to the birds. In a fairy-tale-esque twist, he says that, every time the moon comes out, the grove turns into a chorus of songs.
At the end of the night, the speaker bids everyone (including the nightingale) farewell, but not before reminiscing how his son came to associate nature, and especially the night sky, with joy. He hopes that his son will always enjoy the night sky, even if most people seem to associate night with gloom and doom in the same way they associate the nightingale's song with sorrow.