In Lyon during the year 1943, Fontaine, a courageous member of the French Resistance, finds himself in a precarious situation when he leaps from the vehicle transporting him to Montluc prison. Unfortunately, his gamble doesn't pay off as he is swiftly captured by German soldiers, who subject him to a brutal beating before locking him away. Throughout his harrowing experience in prison, the chilling echoes of gunfire signify the executions of his fellow inmates, haunting Fontaine as he navigates his imprisonment.
Initially confined to a cell situated on the ground floor of Montluc, Fontaine cleverly communicates with his immediate neighbor by tapping on the wall. He also manages to converse with Terry, a fellow inmate from a small group allowed to exercise in a courtyard without supervision. Terry becomes Fontaine's lifeline by delivering letters to his family and comrades in the Resistance, and he even provides him with a safety pin to aid in his attempts at liberation.
After spending fifteen grueling days in his original cell, Fontaine is transferred to a more isolated top-floor cell, and to his relief, he is no longer required to wear handcuffs. Here, he meets Blanchet, an elderly inmate who initially remains unresponsive to Fontaine's wall taps. However, as they bond during their daily chores, Blanchet finally begins to engage in conversation, providing Fontaine with some companionship amidst his bleak surroundings.
Fontaine observes the structure of the wooden door separating him from freedom, cleverly noting its construction of thick boards joined by softer wood. Using patience and ingenuity, he begins chiseling away the joints with a sharpened spoon, meticulously disposing of the wood shavings and disguising his efforts to avoid detection. This slow, calculated effort ultimately enables him to slip into the corridor undetected. To facilitate his escape, he crafts rope from makeshift materials found within his cell.
As rumors start to spread among fellow prisoners that Fontaine may have discovered an escape route, Orsini, one of the inmates who has been aiding Fontaine by signaling the approach of guards, expresses his desire to join the escape attempt. However, Fontaine soon realizes that Orsini's impulsiveness leads to his capture when he makes a reckless bid for freedom during a slop bucket run, resulting in his return to prison and a sentence of execution. In a moment of desperation, Orsini urges Fontaine to fashion hooks to scale the prison walls.
As Fontaine's prison days linger on, doubt begins to creep into the minds of some inmates regarding the feasibility of his escape plan. Despite this, he receives support from Blanchet, who even donates a blanket towards his rope-making efforts. Tensions rise as Fontaine learns of his impending death sentence, and a new cellmate, François Jost, joins him, claiming he has been charged with desertion. Fontaine suspects Jost may be a Nazi plant, yet he decides to build a bond with him for the sake of survival, knowing the alternative could mean betrayal.
Eventually, Fontaine divulges his escape plan to Jost, who reluctantly agrees to assist him, acknowledging the dire situation they both face. Together they strategize, crafting additional ropes for their imminent escape. Under the cover of nightfall, they ascend into the hallway, reaching the rooftop through a skylight. With the noise from passing trains providing a cloak of sound, Fontaine leads Jost across the roof. Upon reaching a critical juncture, he hesitates, his nerves almost getting the better of him. However, after what feels like an eternity, he finally steels his resolve and shimmies across a rope he’s fashioned, dropping down into the bustling streets of Lyon, leaving the confines of Montluc prison behind—at last, the taste of freedom beckons.
