The poem is set on an evening ferry ride from Manhattan to Brooklyn, a half hour before sunset. The ferry is bustling with businessmen in expensive clothes, women with little kids, and workers returning home after a long day. The tide is rushing past the boat, which reminds us of the tides of people and things that rush by the reader throughout the poem.
The New York ports are smoky and crowded with boats from many different countries. Sailors are hanging out in the rigging of their boats and on shore people are yelling and unloading cargo. Sea-gulls are looping and diving through the air. The foundries that produce metal objects glow red and yellow, and their chimneys will keep smoking into the night. And all the while the watery current will continue to ebb and flow, ebb and flow.
Every so often, however, the setting of the poem shifts to us, the readers. The speaker reminds us that we're reading something and we're like, "Hm, that's right, I guess I am reading." Then he says he's watching us, and we check under our tables and inside our closets just to make sure.
The poem seems to get darker as it goes along. Sunset turns to twilight, and a shadow falls across the speaker, too, as he tells us about some of his evil deeds. But somehow it's a comforting darkness, not a sinister one.
At the end of the poem, the speaker points his imaginary finger and takes us through all the sights of the journey one more time. The whole scene seems to obey his commands. Then the scene vanishes and we're left with just generic stuff: "objects," "all things," "parts," and "solids and fluids." If you know what you're doing, you can make a Soul out of these things.