The poem describes a brook that was once part of a rural landscape but has been covered over by a growing city. The brook was strong and full of life, but it has now been confined underground in darkness as a sewer, its natural flow disrupted. The poet wonders if the thoughts and anxieties of the modern city dwellers are in part caused by their disconnection from nature and destruction of natural places like this brook. The poem is a criticism of urbanization and the prioritization of development over protecting natural spaces and environments.