Toni Collette, Angourie Rice, Hugo Weaving, Jacki Weaver
Late on a hot summer night in 1969, Charlie Bucktin, a precocious and bookish 14-year-old boy, is startled by an urgent knock on his bedroom window. It's Jasper Jones, an outcast in the small Western Australian mining town of Corrigan. Rebellious, mixed-race, and solitary, Jasper is for Charlie a distant figure of danger and intrigue. So when Jasper begs for his help, Charlie takes off into the night with him, terrified but desperate to impress. Jasper takes him to a secret glade where Charlie witnesses something terrible: a 16-year-old girl, Laura Wishart, Jasper's girlfriend and the only person he could trust, is hanging dead from a eucalypt tree.
Charlie immediately wants to contact the police. Jasper, however, says they can't. Because of his Aboriginality he is blamed for everything bad that happens in Corrigan and he believes he will surely be blamed for Laura's death. Besides, Jasper tells Charlie, he already knows the murderer's identity: Mad Jack Lionel, the town recluse, a man who it is rumoured killed a woman several years previously and hung her in the local abattoir.
Charlie gives in to Jasper's wishes and together they hide Laura's body, agreeing to keep it a secret and catch the real killer themselves.
Jasper disappears for days and Charlie carries the secret heavily, especially when in the company of Eliza Wishart, his unrequited love and the younger sister of the missing girl. As the townspeople of Corrigan, led by the Sergeant, search for Laura, they get closer to the glade every day.
Charlie struggles to contain what he knows and battles to keep a lid on his over-enthusiastic best friend, the Vietnamese and cricket-loving Jeffrey.
Meanwhile, at home, Charlie's tempestuous mother Ruth dishes out harsh discipline, to which his browbeaten father Wes appears resigned. Charlie feels alone with his secret and his task of helping find evidence to catch the killer. But Jasper reappears at his window one night, they stake out Mad Jack's house together, and Jasper urges Charlie to break in and find the evidence they need.
When the town Sargent finds and interrogates Jasper, Charlie is determined to find the truth and save his new friend. He goes onto Mad Jack Lionel's property and looks for answers. Jasper, meanwhile, escapes the clutches of local police and returns to Charlie's house at night, badly beaten. Jasper is pleased, however, when Charlie offers him the interesting evidence he's found.
In town, things are beginning to look up after Jeffrey, previously bullied and excluded, helps the local junior cricket team win against their archrivals. But their newfound cheer is stripped away when racist locals vandalise Jeffrey's family home.
The night of the town's New Year Fair, Charlie and Jasper decide it is time to act and confront Mad Jack. What they discover is astonishing: Mad Jack is not the killer and he reveals instead a little-known secret about Jasper's parentage - he is Jasper's grandfather. Jasper's father, with whom he has little contact, kept this secret from Jasper to punish Jack for accidentally killing his wife Rosie in a car crash years ago.
Charlie, determined now to tell Eliza what happened to her sister, takes her to the secret glade, but finds that Eliza already knows the truth. Holding a letter from her sister, Charlie and Jasper learn what happened to Laura: her death was a suicide due to her father, a respected town leader, molesting her for years. Jasper, racked with anger and despair, dives into the river. When Jasper doesn't reappear from the water, Charlie dives in, pulling his friend from the dark waters and back to safety.