Within the confines of a strict, all-girls English boarding school (circa 1930s), a clique students participate on the swim team not only to pass the time, but to be close to their swimming instructor, the enigmatic, yet charismatic, Miss G (Eva Green). While Miss G originally encourages their idolization and crack (crush) on her, the teachers attention is quickly focused on the arrival of an exotic and beautiful Spanish foreign pupil, Fiamma (María Valverde). As the new girl rebuffs her classmates, and further rejects Miss Gs interest, her teammates begin to grow jealous of Miss Gs fascination with Fiamma, and resent the latters distain of their instructor, accumulating in the inexplicable disappearance of Fiamma.