In the quiet town of Ithaca, located in upstate New York, Dr. John Mathewson finds himself at the center of a significant discovery when he stumbles upon a revolutionary method for refining plutonium with unparalleled purity. Seizing this rare opportunity, the United States government adopts a guise as a medical corporation, providing him with an advanced laboratory. As John acclimates to his new environment, he unexpectedly meets Elizabeth Stephens, a real estate agent, while on the hunt for an ideal apartment. What starts as an innocent attempt to charm her takes an unforeseen twist when he invites her teenage son, Paul, for a tour of the lab, hoping to leave a positive impression.
However, Paul's keen intellect and fascination with science set him apart from the typical teenager. When he accidentally discovers an extraordinarily rare five-leaf clover within the lab's grounds, his suspicion about the true nature of the facility's activities deepens. Alongside his girlfriend, Jenny Anderman, who dreams of being a journalist, they decide to investigate further, culminating in a daring plan to steal a sample of plutonium to serve as proof of their findings.
Determined that having plutonium alone won't suffice to unveil the lab's covert operations, Paul and Jenny design an ambitious scheme to construct the world’s first privately developed nuclear device. They cleverly disguise their experiment as a school project for the New York Science Fair, with Paul convincing his mother and classmates that the focus is on hamsters raised in darkness. Meanwhile, John remains blissfully unaware of the brewing turmoil, increasingly secure in the lab's capacity to maintain its façade.
Things take a dramatic turn when lab officials realize that a crucial container of plutonium has mysteriously been exchanged for a bottle of shampoo embellished with glitter. Prompting swift action, a military investigative unit, led by Lt. Colonel Conroy, arrives on site, quickly pinpointing Paul as the prime suspect in the theft. As agents close in on him, John feels the weight of responsibility and arranges a discreet meeting with Paul, hoping to persuade him to surrender the explosive device before events spiral out of control.
Despite John’s intentions, Paul and Jenny find a way to evade capture during the chaotic science fair, leading them to devise another strategy to expose the lab's dark secrets. In a bold move, Paul returns to the laboratory bearing the nuclear device, encircled by snipers and agents ready to take action. Amidst stalled negotiations and rising tensions, John attempts to advocate for Paul, insisting the teenager does not pose a real threat.
As the radioactive energy from the plutonium within the device takes hold, the countdown clock springs to life, its ominous rhythm quickening. Paul suggests relocating the bomb to a nearby quarry, but John's admission that he underestimated the ramifications of his plutonium refining ignites fear in everyone present: a detonation would unleash destruction far exceeding that of the Hiroshima bombing.
Amid escalating panic, all involved – including Paul, John, and Conroy – drop their weapons and join forces to neutralize the dangerous device. With time slipping away, they exploit every ounce of knowledge and collaboration to disassemble the bomb. In a heart-stopping climax, they achieve successful deactivation just seconds before disaster strikes.
As calm returns, Conroy prepares to detain Paul. Yet, John stands firm against compliance. With a dramatic gesture, he throws open the laboratory doors, unveiling a gathering crowd outside that includes Jenny and the media. The scene fades to black, leaving Paul to depart unhindered, creating a lingering sense of uncertainty and unspoken repercussions in his wake.
