In the sweltering summer of the 1970s in Savannah, Georgia, a group of rebellious teenagers at St. Agatha's Catholic School escapes into their own subversive universe. The story follows Francis Doyle and his pals, Tim Sullivan, Wade Scalisi, and Joey Anderson, as they navigate their days filled with marijuana, whiskey-fueled adventures, and a budding interest in girls. Their antics, like stealing the school's statue of St. Agatha and hiding it in their makeshift clubhouse, reveal their deep discontent with the drudgery of student life.
As Francis embarks on a journey of self-discovery, he becomes intrigued by Margie Flynn, whose arrival sparks upheaval within their group. A love note penned by Tim, which Francis misinterprets as a genuine proclamation of love, catalyzes Margie's entry into their tightly-knit circle. As Francis and Margie's relationship grows, he is torn between his devotion to his friends and his burgeoning feelings for her. This marks the beginning of a gradual unraveling of their once unbreakable bond.
The boys’ creative refuge, a comic book named The Atomic Trinity, serves as an escape from their troubling reality. This imaginative realm, featuring characters like Brakken, Captain Asskicker, and Major Screw, captures their aspirations and fears. Meanwhile, Nunzilla, a satirical take on their irritable teacher Sister Assumpta, alongside Sorcerella, a character inspired by Margie, blurs the lines between their actual lives and their whimsical fantasies.
Their mischief takes a chaotic turn during a school trip to the local zoo, where Tim and Francis hatch a wild scheme to drug a cougar and deliver it to Sister Assumpta's office as a prank. However, as their plan begins to spiral out of control, the friendship crumbles, reducing their group to an unexpected trio of Margie, Tim, and Francis. Within this fragile dynamic, Francis discovers Margie's traumatic past involving her brother, Donny, which comes to light shortly after Donny's violent outburst against Tim. This chain of events leads to both Tim's and Francis's suspension from school.
The Atomic Trinity, their beloved comic book, inadvertently becomes part of the fallout when Donny seizes it and shows it to Sister Assumpta. The graphic depictions, filled with violent and blasphemous imagery, propel Tim and Francis toward the brink of expulsion from St. Agatha's. In a final act of retribution, Tim, Francis, Wade, and Joey plot an audacious scheme to steal a cougar from the zoo to cover up the chaos they caused. Under the veil of night, they manage to tranquilize the beast with a makeshift sedative.
Driven by bravado, Tim recklessly climbs over the fence into the cougar’s enclosure, where a tragic confrontation ensues, resulting in his untimely death at the hands of a lurking cougar. In the wake of this senseless loss, Francis delivers a poignant eulogy at Tim's funeral, drawing from the lines of "The Tyger" by William Blake, verses that Sister Assumpta had previously condemned. This moment accentuates the fleeting nature of life and humanity's vulnerability.
In a dark twist of fate, Francis later leaves the anthology of poems at the spot where they had previously stolen the statue of St. Agatha—an homage to their sanctum. In remembrance of Tim, he begins a new comic series entirely devoted to a character inspired by his fallen friend, naming him Skeleton Boy—a legacy that will forever linger in their shared history.
