Goblin Market is about two close sisters, Laura and Lizzie, as well as the goblin men to whom the title refers, and another girl named Jeanie.
Although the sisters seem to be quite young, they live by themselves in a house, and are accustomed to draw water every evening from a stream. As the poem begins, twilight is falling, and as usual the sisters hear the calls from the goblin merchants, who sell fruits in fantastic abundance, variety and savour. On this evening, Laura lingers at the stream after her sister has left for home. Wanting fruit but having no money, the impulsive Laura offers a lock of her hair and "a tear more rare than pearl."
Laura gorges on the delicious fruit in a sort of bacchic frenzy, then comes to her senses and, after picking up one of the seeds, returns home. Lizzie, waiting at home, and "full of wise upbraidings," reminds Laura about the cautionary tale of Jeanie, another girl who, having likewise partaken of the goblin men's fruits, died just at the beginning of winter, after a long decline.
Night has by then fallen, and the sisters go to sleep in their shared bed.
The next day, as Laura and Lizzie go about their work in the house, Laura dreamily longs for the coming evening's meeting with the goblin men. But at the stream that evening, as she strains to hear the usual goblin chants and cries, Laura discovers to her horror that, although Lizzie still hears the goblins' voices, she no longer can.
Extract from a longer explanation: