Natalie, a famous American actress, has a secret fascination for corporal punishment, and is an avid reader of reformatory discipline stories. Wanting to experience things first hand, she voluntarily enrols herself at the Goodwood Reformatory in England, claiming she is undertaking research for a future acting role.

At Mercy Night, along with the other genuine inmates, she presents her formal petition to the Reformatory's strict Board of Governors, a procedure which excites her greatly. However, rather than the mere formality she was expecting, Natalie is shocked to discover she has not been found innocent, but that Judge Hardcase, merely deciding she looks guilty, has sentenced her to an indeterminate detention for real! Now, reclassified as a delinquent, she is forced to prepare the birch she is to receive while secured to a punishment horse in front of an invited audience on Justice Night.

Following the birching, Natalie is subjected to a number of further humiliations and degrading punishments at the hands of Judge Hardcase. Although mortified by her treatment, she is also very excited by it and frequently pleasures herself as she recalls her punishments. Eventually, Natalie is given the opportunity to have her charges dropped and to leave the Reformatory and return home. Just what will she do?