A narcissistic trainer at an elite fitness centre injects a dangerous, contaminated steroid to make fast money. The overdose triggers a violent mutation, turning the luxury gym into ground zero for a zombie apocalypse-an unstoppable outbreak. Authorities move in instantly sealing the building, surrounding it with armed police, and unleashing a frantic media storm. Inside, a humble fitness trainer arrives to pick up his girlfriend-a Zumba instructor-teaching young students on the third floor. He begins fighting mutated gym-goers and confronting his long-time rival, now transformed into an unstoppable zombie monster. With the world against them, the couple must rely on nothing but courage and each other.