Canudos was a small village in northeastern Brazil, founded by the messianic leader Antônio Conselheiro and massacred by a powerful army until the death of the last of its 30,000 inhabitants, on October 5, 1897. The film tells the story of the Canudos massacre from an English cannon, nicknamed by the backlands people "A Matadeira", which was transported by twenty teams of oxen through the backlands to fire a single shot.

In Rio Grande do Sul, the newcomer intern Paula sees the schizophrenic Dante Becker and she decides to study his case for her graduation work in the university. She learns that Dante was left in the institution ten years ago and has been abandoned by his family, friends and even the doctors and his files are lost. Her supervisor retrieves the name of Dante's father Gregório and the women Renê Heller and Berenice that had visited him in the past and she interviews them to discover what happened with Dante.