As the prankster group led by "PrankMonkey69" Brady Mannion, along with his friends Sam Fuller and Jeff Mosley, gain notoriety from their clever prank phone calls, particularly the one that fooled Mrs. Kolbein into believing an intruder had breached her home, their YouTube channel is thriving. In a bid to build on their recent success, Brady decides to pay a weekend visit to Sam, sparking the duo's enthusiasm for crafting even more devious pranks. Their latest scheme involves a pizza delivery to Larry, Sam's neighbor, which Jeff is tasked to deliver, all while juggling his relationship with Peyton.
Things, however, spiral out of control when Jeff becomes uncomfortable with their antics, feeling that their light-hearted humor has turned into something more sinister. Meanwhile, a mysterious individual named Mr. Lee incessantly calls Sam and Brady, initially disregarded by the pranksters until he reveals alarming details about their personal lives that sends shivers down their spines. The tension heightens further when Peyton arrives unexpectedly with a pizza she claims to know nothing about, leading to the shocking discovery that Jeff is missing right after delivering the order.
The harassing phone calls soon escalate into threatening texts, and the situation reaches an unimaginable climax when Mr. Lee sends disturbing videos, one of which depicts him suffocating Roy with a plastic bag. As fear envelops the group, Sam discovers a helpless Jeff bound and gagged at the back of their home, who tragically dies despite their desperate attempts to save him. The horror deepens when Mr. Lee makes a sinister proposal to Brady: kill Sam in exchange for the safety of his parents, alongside chilling evidence that Peyton has also been captured.
With Sam's suspicions on red alert, he confronts Brady about a covert conversation with Mr. Lee, igniting a fierce fight between the two. After subduing Brady, Sam takes control of the situation by restraining his friend and plunges into a desperate search for answers. A shocking discovery reveals a childhood photo and the name "Izzy," triggering Sam to look into a social media friend request that unveils Mr. Lee’s year-long obsession with their group.
As revelations pour in, it becomes clear that Brady and Peyton were having an affair, driving Sam's rage to new heights as he physically confronts Brady yet again. However, just as Sam begins to piece together the mystery, he realizes Mr. Lee has already killed Brady's parents, leading Sam to suspect he must act quickly to save Peyton. Yet just as he steps outside for help, Brady betrays him, locking the door behind him and igniting doubts about their friendship.
While in search of their captor, Sam discovers a surveillance van containing the imprisoned Peyton and manages to rescue her, unaware that Brady has been deceived into believing he was aiding them. Meanwhile, Brady’s grim encounter with Jeff’s corpse reveals a shocking truth: Mr. Lee had impersonated Jeff while hiding in plain sight. Just when he grasps the magnitude of the betrayal, Mr. Lee ambushes him.
Amidst the chaos, Sam attempts to save Brady while sending Peyton to get help. But when he follows her screams, he unintentionally stabs Brady, who was masquerading as Mr. Lee. The revelation of the setup leaves the two friends shattered as Mr. Lee’s motives unfold, detailing his quest for vengeance for the tragic death of his family due to the boys’ pranks gone awry.
As the authorities arrive on the scene, they misinterpret the situation, apprehending Sam, who is now deluded as the prime suspect. In the heart-wrenching aftermath, Brady confronts the despairing truth of their ordeal, amplifying the cycle of retribution set into motion by Mr. Lee, who sets his sights on the next unwitting target.
