Sam is a young boy recovering from an operation that has left him mute. He lives with his mother and sister, Katie – all dutifully cared for by Aunt Dettie. As he struggles with his inability to speak, his mother begins to date again, and Dettie reacts very badly. After an unexpected phone call, she packs Sam and Katie into the backseat of her car and tells them that she's taking them to be reunited with their estranged father. But as Dettie drives from Sydney to Perth in the middle of a sweltering and dangerous bushfire season, her behaviour becomes increasingly erratic and soon the children begin to realise that there is something very wrong. Voiceless, Sam can only watch helplessly as the trip becomes a nightmare…