Struggling screenwriter Marty finds himself entangled in the Los Angeles criminal underworld after his oddball friends kidnap a gangster's beloved Shih Tzu. Marty's goal to finish his screenplay titled "Seven Psychopaths" hits an impasse, not only because of his alcoholism and lacking inspiration but also due to the chaos that ensues from his friends' dog-napping scheme. The gangster, Charlie, is naturally unhinged and vicious, and his attachment to his pet draws him into a relentless and violent search. Marty's friends, Billy and Hans, meanwhile, are accidentally in the business of dog theft and extortion, which complicates their lives far beyond what they had anticipated.

As the paths of writer and gangster cross, Marty's experiences with the shady characters around him begin to provide the inspiration he needs for his script. Each of these "psychopaths" contributes bizarre and darkly comical stories to his life and writing, blurring the lines between Marty's reality and the fiction he is trying to create. The situation escalates with the introduction of other colorful and dangerous individuals, each with their own twisted tales and motivations. The confluence of Marty's creative process and his friends' criminal misadventures leads to a series of unpredictable events that threaten to spiral out of control, putting their lives and Marty's artistic aspirations in jeopardy.