|Isobel Meikle-Small||Young Kathy|
|Ella Purnell||Young Ruth|
|Charlie Rowe||Young Tommy|
|Charlotte Rampling||Miss Emily|
|Sally Hawkins||Miss Lucy|
Friends Kathy, Tommy and Ruth grow up together at a seemingly idyllic boarding school in the English countryside. When they leave the school and the horrible truth of their true purpose is revealed to them, they must simultaneously confront deep-seated feelings of love, jealousy and betrayal that threaten to tear their friendship asunder.