A professional hitman in Los Angeles finds himself poisoned with a mysterious synthetic compound that slows down his heart rate and will eventually kill him if his adrenaline level drops. The toxin allows him no time for a slow-paced investigation or a cautious approach to find an antidote. Instead, he is forced into a frenetic pursuit of survival by whatever means necessary.

To maintain his elevated adrenaline and keep his heart beating, the hitman embarks on a non-stop quest for vengeance and answers, seeking out the individuals responsible for his dire situation. His journey is a chaotic rush through the city, resorting to extreme measures and behaviors to stay alive. With time running out quickly, he must also navigate the complex relationships in his life while on this high-stakes race against his own biology.