It's Chicago in 1968, and Sam's life is suddenly very complicated. His father is a civil rights activist who works alongside Dr. Martin Luther King Jr. He preaches passive resistance, non-violent protest, and all Sam's life, he and his brother Stick (Steve, really, but Sam calls him Stick) have been right there, attending protests and making signs and sealing envelopes.
But Sam starts dating a girl from the projects, and he finds out that his brother is involved with the Black Panthers, a group of militant black activists who are willing to take up arms, if need be, to make equality happen. When Dr. King is assassinated, Sam finds himself questioning the efficacy of his father's methods--he's angry, he's hurt, and he sees his brother actually doing things instead of just talking about them, the way his father seems to.
Ultimately, after a series of tragic and near-tragic events that rock Sam's entire world, he has to decide whether to be the rock (his father), unmoving in the face of extreme pressure, or the river (the Panthers), which moves itself and pushes against its obstacles.