The Winslow Boy is a drama film based on a play of the same name by Terence Rattigan. The movie is set in early 20th century England, where an upper-middle-class family, the Winslows, is rocked by the news that their 14-year-old son Ronnie has been expelled from the Royal Naval Academy for allegedly stealing money from a fellow student.
Ronnie denies the charge, and his father Arthur Winslow believes him. Convinced of his son's innocence, Arthur decides to pursue justice, despite the risks involved. He hires the brilliant and charismatic lawyer Sir Robert Morton, who takes up the case and starts investigating the matter.
As the case progresses, it takes a toll on the Winslow family, both financially and emotionally. Arthur exhausts his fortune trying to prove his son's innocence, and Catherine's engagement is called off due to the scandal. Meanwhile, Sir Robert's tactics and motives are called into question, and his relationship with the Winslow's daughter, suffragette and feminist-minded Catherine, becomes complicated.
Ultimately, the case goes to trial, and the family's character and determination are put to the test. The outcome of the trial and Ronnie's fate hang in the balance, and the Winslow family must decide what they are willing to sacrifice for the pursuit of justice.