After a wealthy philanthropist expresses an unusual interest in a ring found by her niece Annabelle, Miss Fritton explains that she's descended from a pirate who, in 1598, stole treasure from another: the philanthropist's ancestor. This discovery sends the racuous girls of St. Trinians on the hunt for buried treasure.

Talulah Riley
as Annabelle Fritton

Rupert Everett
as Camilla Fritton / Captain Archibald Fritton / Fortnam Fritton

Gemma Arterton
as Kelly Jones

David Tennant
as Captain Lord Pomfrey / Sir Piers Pomfrey

Colin Firth
as Geoffrey Thwaites

Jodie Whittaker
as Beverly

Juno Temple
as Celia

Tamsin Egerton
as Chelsea Parker

Toby Jones
as Bursar

Sarah Harding
as Roxy