Does the idea of a poetry-reading contest strike you as a snore? Snap out of it. Slam, a breakthrough debut in features from documentarian Marc Levin, cuts to the grieving heart of a hip-hop nation forged out of grit and grace. Ray (Saul Williams) rots in a Washington, D.C., jail, charged with drug trafficking — another black male reduced to a statistic in the city's ghetto.

Except that Ray has a voice. In his cell and in the prison courtyard, he raps out his rage. The words, of Ray's own composing, spill out with pent-up passion. This is no West Side Story, at which audiences gasped in shock as gangbangers burst into balletic dance. Rap has attuned us to the poetry of the streets. When Ray talks, people listen.

Behind bars, Ray finds help in arranging bail from Hopha (Bonz Malone), a gang leader, and encouragement from Lauren (Sonja Sohn), who runs a writing workshop for prisoners. Ray's feelings for Lauren deepen after his release; she invites him to compete in a poetry slam, in which Ray's voice joins others in a chorus of self-expression.

Any cornball contrivances in the plot dissipate in watching the knockout talent of Williams, a performance artist with the exhilarating fire that only the best actors possess. Williams and Sohn, another urban poet, wrote their own material and give the film an authenticity matched by Levin's cinema vérité handling of the traps facing Ray: the inner city, a cell, a closed mind. No wonder this emotional powerhouse won the 1998 Grand Jury Prize at the Sundance Film Festival. Slam is a different kind of prison movie: It offers art as a way out.