Trouble is coming, and the Bag Man is bringing it.
One fine day, literature professor Byron Williams is returning home from work when he suddenly opts to give a ratty bum a ride in his Mercedes—and he's just about rejoicing at the opportunity. Weird and out-of-character for the serious-minded professor who secretly writes poetry no one else has ever seen—but that’s nothing compared to what awaits him at home. The Bag Man hops out of Byron's car and informs Byron that his wife is pregnant. Byron is amazed at the man's knowledge—and even more amazed to walk into his house, find his other children in a tizzy, and his wife upstairs on the bed, suddenly enormously pregnant and about to give birth.
As if in some sort of dream, Byron delivers the baby—and the Bag Man walks into his house, collects the child, and stuffs him into a bag. In the aftermath of this traumatic event, Byron discovers that neither Nadine nor the children remember the Bag Man or the baby—he alone remembers what happened. And yet he can say nothing—for who would believe that he had delivered his wife's baby, when even she had no recollection of such a thing?
For the residents of Baldwin Hills, a middle-class African-American community, nothing will ever be quite the same again. Out playing with a friend, Cecil "Ceese" Tucker finds an infant shoved in a shopping bag. He takes the baby to a local spinster (and nurse) named Ura Lee Smitcher who ends up adopting the boy, and Ceese becomes his babysitter and authority figure. Ura Lee names the boy Mack Street. Mack grows up to be a sweet, if somewhat odd, boy, full of visions and what he calls the "cold dreams." The cold dreams seem to be the window into the dark desires of others in the neighborhood—dreams that often come true in twisted, horrible ways. When a young girl dreams of being a fish, she is subsequently found trapped inside her father's waterbed, and he is charged with attempted murder.