The speaker has vague, anxious thoughts about his future as he walks on the moors one day, young and in good health. As he puts it, a "dim sadness" overtakes him, and he worries

there may come another day to me—

Solitude, pain of heart, distress, and poverty.

As chance or fate would have it, he stumbles on a very old man, the oldest he has ever seen, bent over, poor, and frail. The man seems to embody in the flesh all that the speaker fears about his own future.

The speaker talks to the man, who he finds out is a leech gatherer. The man is very poor and wanders from place to place. He tells the speaker that the supply of leeches to gather and sell is much less than it once was, making his hard work that much harder than it once was.

The hard life of the aged leech gatherer troubles the speaker at the end of the poem. He thinks: