The film opens with the character Chorus, portrayed by Derek Jacobi, who sets the stage by walking through a deserted film studio. He introduces the narrative before dramatically opening the doors to the main action, reappearing intermittently to offer insights and drive the plot forward.
Act 1 unfolds in the early 15th century, specifically the year 1422 A.D., where the Bishop of Ely (Alec McCowan) and the Archbishop of Canterbury (Charles Kay) plot to divert the attention of young King Henry V (Kenneth Branagh) from a decree threatening the Catholic Church's property. They persuade him to consider an invasion of France using the claim that he is the rightful heir to the French throne, arguing that the Salic law unjustly denies him this right. With the backing of noblemen The Duke of Exeter (Brian Blessed) and Westmoreland (Paul Gregory), they convince Henry to declare war, leading to a confrontation with Mountjoy (Christopher Ravenscroft), the Dauphin's envoy. The Dauphin's disdainful gift of tennis balls abates Henry's initial anger but ignites his resolve to claim his birthright.
In Act 2, King Henry cunningly exposes three of his high-ranking officers—Richard, Earl of Cambridge, Sir Thomas Grey, and Henry, Lord Scroop of Masham—previously plotting to betray him. By feigning an inquiry about an insolent offender, he prompts their own confession of guilt, leading to their arrest for treason. After a violent display, Henry orders their execution before embarking across the English Channel. Meanwhile, in France, King Charles VI (Paul Schofield) and his court debate Henry's threats. The Dauphin's bravado is mitigated by the concerns of his peers over Henry's formidable heritage and prior English victories.
In Act 3, Henry delivers an inspiring speech to his troops as they besiege the fortified French city of Harfleur. When the Dauphin fails to send reinforcements, the governor capitulates under Henry's assurance of mercy. Concurrently, Katherine (Emma Thompson), the French princess betrothed to Henry prior to the conflict, struggles to learn English, observing her father’s anxiety regarding the war. Following a series of grim encounters, Henry asserts the strength of his beleaguered forces when confronted by a French herald demanding his surrender.
During Act 4, the eve of the famous Battle of Agincourt on October 22, 1415, reveals a stark contrast between the impatient French nobility and the solemn English troops. Disguised, Henry mingles among his soldiers, reflecting on his leadership and the bloodshed to come, leading to an intense encounter with Williams, where they agree to a duel for the next day. Despite being heavily outnumbered, Henry’s fervent St. Crispin's Day Speech boosts his soldiers' morale, and the ensuing battle showcases the devastating effectiveness of English archers. As chaos unfolds, the French suffer catastrophic losses, ultimately culminating in their surrender.
Act 5 sees negotiations for Henry's royal union with Katherine, symbolizing peace between England and France. Their private conversation reveals Henry's sincerity and affection for her, and he hopes for a future where the two kingdoms are united. As the treaty is finalized, the Chorus returns to reflect on the historical ramifications, culminating in the eventual loss of the French crown by Henry VI, underscoring the film's exploration of ambition, leadership, and the tragic cycles of history.
