Nuneaton, 1850. Growing up on a canal boat has meant life for young Saffie Doyle has been hard. Her mother, Olivia, was cast out by her well-to-do family when she fell in love with Saffie's father, a lowly boatman named Reuben. But as the years have passed, Reuben has become a bitter and cruel drunk, forced to work for the local crook, Seth Black, to keep their family afloat. Saffie always dreamed of becoming a teacher, despite her father's insistence that she had no need to read and write. Keen to nurture her ambitions, Olivia hoped to introduce Saffie to a childhood friend - the kindly and wealthy Marcus - who runs a free school for the local children, but when Olivia falls ill, she's unable to. One night, Saffie's 17-year-old brother and her father go out on a job with Seth Black and never return home. Saffie is forced to place her dreams on hold as she steps up to look after her family. With her younger siblings relying on her, will Saffie ever be able to live the life she hopes for?