Lila Taylor Spreitler Jenkins arrives at Devil's Lake, North Dakota, to help greenify an old house owned by her sorority at Laramore University. Lila hitches a ride from Ozzie Mark Holton Jones and shares that her mother, Tory Redding Heather McDonald, died the year before from cancer. On the way, Ozzie accidentally drops his phone while unloading Lila's luggage and heads back to retrieve it. A spray of water from the old well reanimates the Leprechaun Linden Porco, who bursts out of Ozzie’s torso after a fierce fight, seizing the gold coin Ozzie swallowed twenty-five years earlier.
Lila meets her sorority sisters—Katie, Rose, and Meredith—along with Katie's ex-boyfriend Andy and Matt, a wannabe filmmaker. Katie, an eco-minded optimist, and Rose, the group’s outspoken leader, are joined by Meredith, who drinks a little too much and often clashes with Lila. Meredith’s presence, and her heavy-handed attitude, leads to tension as she insults Lila's mother for her supposed fear of monsters. That night, Lila is left to sleep while visions of Zombie Ozzie haunt her dreams. The next morning, Katie and Andy install a solar panel, and the Leprechaun learns that his powers are weakened by the loss of gold, prompting him to decide that killing is his quickest fix.
That night, the Leprechaun reveals himself to Lila and Meredith, who capture a photo of the creature while Matt and Rose doubt the strange claims. Andy also encounters the Leprechaun, who cuts him in half with the solar panel. Meredith and Lila sneak back inside the house to recover the car keys, but Meredith locks Lila in the basement and confesses that she struck a deal with the Leprechaun to capture Lila and leave the others alone. The others mistakenly believe Lila is dead and leave, but they soon learn Meredith’s true intentions.
Meanwhile, Lila receives help from Ghost Ozzie, who guides her to the Leprechaun’s weakness and the basement’s exit hole. When the Leprechaun catches up to the group on Matt’s drone, a crash into a tree forces them to flee, and Meredith’s fate is sealed as the Leprechaun exposes a loophole he crafted to keep killing. The monster slows Meredith with sprinklers and ends her by forcing a sprinkler faucet into her mouth. Matt tries to slow the Leprechaun with the drone, but the machine is hijacked and kills Matt with its blades.
Rose and Katie catch up with Lila and follow a treasure map that Ghost Ozzie helped uncover. The trio discovers a pickup truck hiding the gold, but Rose confesses she already used some of it to fund the greenification project. To fool the Leprechaun, Lila stuffs the pot with tampons and offers the gold back, but the demon sees through the ruse. Lila then traps the Leprechaun in a circle of iron objects, a classic leprechaun weakness, and hatches a plan to finish him off. Katie restores power as Rose crafts clover juice.
Lila feeds the Leprechaun the clover juice through a hose stuffed into his mouth, causing him to explode. Rose offers to clean up, but the Leprechaun multiplies from chunks of his own body, and Rose fights to hold him off—ultimately falling victim as the creatures overpower her and she is impaled on a trophy. The Leprechaun re-forms just as Lila and Katie learn of Rose’s death. In a final move, Lila surrounds the Leprechaun’s feet with gold and electrocutes him, blowing up the house in a spectacular blaze. Lila and Katie escape, covered in green slime, as the Leprechaun hitchhikes a ride on a chicken truck bound for Bismarck, North Dakota to reclaim his gold.
