1925. Fifteen-year-old Catherine Quick longs to strike out into the warm waters of her Australian home just as she's done since she was a tiny child. But now living in London with her aunt Louisa, Catherine feels that everything she values has been stripped away.
Louisa, a busy surgeon who fought boldly for women's equality, wants Catherine to pursue an education to ensure her future freedom. Since Catherine arrived, however, Louisa can't put a foot right and she is finding it harder to block painful memories from her past.
A chance encounter leads both women to New York where Catherine can test her mettle against the first women in the world to swim the English Channel, and where Louisa can come to an understanding with her niece and with herself.