Mary is onboard a convict transport ship on route to Australia and Polly, a streetwise convict in charge, makes Mary life harder. Ensign Grenville gives Mary a chance to escape the prison below, but he is furious when she turns down his offer. This leads him to what revenge which backfires when Mary cuts a soldier in self-defence. Worse is to come though when there is talk of a mutiny. (thetvdb.com)