The book begins in the year 1862. It is here that we learn that the main characters and the other slaves suppress their “silent thunder." An adult slave explains that your silent thunder comprises your thoughts and desires, anything that makes you feel good.
This can be interpreted as the deconstruction of one’s identity in response to the blatant violence of slavery, and the two child characters struggle against this destruction of their self.
We soon learn that Rosco has broken the law and learned how to read from overhearing the lessons of his Master’s son, Lowell Parnell. Roscoe compounds his crime by teaching his younger sister Summer to read. It is here that Pinkney, in her clever writing style, slips in shocking facts of the brutality of slavery, as Summer learns to recognize her first letter, the ‘P’ which her Master Gideon Parnell used to brand her as his own. As we view this and the other injustices experienced by the slaves through their own eyes, we gain a better understand of what it must have been like to be a slave in this era.
As the story progesses, we learn that Rosco’s own “silent thunder," his desire to be free, is propelled by his yearning to enlist in Union arms, and, through Lincoln’s Emancipation Proclamation, become a freeman. As well, Summer grows up quickly through the terrible secret about herself that she learns from her Mama.
The book also teaches another horror of slavery, that the slaves were used not only for physical labor but also for sexual pleasure. The types of casual brutalities expressed in the novel serve only to reinforce the fact that slavery was an awful institution. There is a thrilling conclusion when Rosco and his friend Clem face a decision and a challenge about their future.