Ray "Cuda" Medina is an MMA Champion, and his old street gang, who now has ties to a Mexican Cartel wants to cash in on his fame.

Years ago, Ray left Los Diablos and moved to Hong Kong to avoid a Grand Theft Auto charge. With the help of his wife, Regina, he regained his self-respect and made a name for himself in the MMA world. Tonight, Ray fights for the Far East Championship title, then plans to return to the U.S. for his first North American match. But, unbeknownst to Ray, whatever he will do stateside has already been arranged by his old gang Los Diablos and the Mexican cartel that now controls them.

Thanks to the Cartel, Los Diablo’s criminal enterprises are worldwide. Pablo, second in command of the Diablos, has come to Hong Kong to bring Ray back to the gang and to collect payment for the cartel's human trafficking operation. The gang plans for Ray to mule the money from their enterprise. They will document the crime and have Ray on the hook for their continuing criminal activities. Done with a life of crime, Ray refuses.

Upon Ray and Regina's return to the United States. The Diablos attempt toreverseRay's decision not to work with them by kidnapping Regina and laying the blame on their rival gang, the South Side Cobras. They assume Ray will seek their help finding Regina, accept their protection, and fall into line as any good Diablo should.

Again, Ray refuses to yield. Instead, his street warrior instincts kick in as he confronts his old gang. Unfortunately, the plan fails, and he and his brother become prisoners of the Diablos. For Ray, this is just another obstacle to overcome. Tapping into his martial arts training, he escapes, which yields dire consequences for his brother. For failure to deliver Ray's loyalty, Miguel is executed.

The Diablos and the Mexican Cartel had set their sights on controlling Ray's MMA career. Outraged at Ray's continued refusal to do the gang's business, Angel the imprisoned psychopath leader of Los Diablos, orders Ray and his father's death. As a peace offering for not delivering Ray's loyalty, Regina is to be given to El Jefe, the head of the Mexican Cartel.

A member of the Diablo's tips off Ray Sr. that his life is in danger and Regina's location. With the gang closing in, Sr. sets about finding his son. Once they are united, they learn of Miguel's death.

Distrustful of the authorities, Ray and Ray Sr. take it upon themselves to save Regina and avenge Miguel's death. But time is not on their side. Pablo and Regina are already in transit to Mexico. When a flat tire forces Pablo to open the trunk, Regina who trained with Ray for many years marshals her fighting skills and almost escapes her captor. After the failed attempt, Pablo crosses the border with Regina. Lost in a city, he does not know he searches for El Jefe's location. Frustration and anger set in as he navigates through the city's Day of the Dead celebration. Finally, after hours of battling crowds, dealing with deadends, and hitting a member of the parade, Regina is delivered to The Boss. It quickly becomes apparent the peace offering has not been well received, and Pablo is in trouble. All these events and delays have given Ray and Ray Sr. time to catch up with Pablo.

When they arrive at El Jefe's mansion, they knock out the guards that patrol the perimeter of the house and enter through the kitchen door. The ensuing fight alerts The Boss that there is a problem, and he sends one of his bodyguards to investigate. As the battle continues in the kitchen. Regina breaks free of her restraints and takes down the remaining guard with a hammer fist. Regina then knocks Pablo to the ground. El Jefe stands frozen behind his desk till she is gone, then reaches for his pistol. Regina runs to the back of the house. Dazed and confused, Pablo wakes up. El Jefe addresses him while brandishing his weapon in his face. "You brought this here. If you don't fix it, I will kill you."The Bossexits through the front door and disappears with a bodyguard.

Pablo enters the kitchen. Ray fires a weapon taken from a guard he has knocked out and misses. Pablo runs from the house and disappears into the darkness. Ray gives chase with police sirens wailing in the background. On the city street, Ray sees Pablomixing with the parade members. Ray gives chase. Pablo runs down a side street and is lost in the shadows. Pablo watches Ray'sgrowingfrustration with a smile from a nearby rooftop as he silently moves away.

Regina and Ray Medina Sr. search for Ray. Pablo spies them from his position on a low rooftop. Waiting for the right moment, Pablo jumps on Ray Medina Sr., knocking him to the ground and injuring his knee. Pablo snatches Regina up by the hair. She responds with a kick to Pablo's face. He lets her go and reels back. Regina delivers a combination of blows that stuns Pablo momentarily. He is briefly impressed. Pablo quickly recovers and quips, "So you want to fight?" Regina holds her own, but is no match for Pablo's size and is knocked out cold. Pablo turns his attention to RayMedina Sr., who staggers to his feet. Ray approaches as Pablo kicks his father. Ray Sr. cries out in agony. Ray raises the pistol and pulls the trigger. The weapon jams. Pablo is surprised at Ray's stealthy arrival.

He moves swiftly to kick the gun from Ray's hand. A punch sends Ray to the ground. The two men fight. They each draw blood. At first, Pablo seems to have the upper hand. He knows Ray has a broken rib and exploits it. However, Ray's training proves the real advantage as the fight continues. Ray Medina Sr. finds the pistol on the ground. He picks up the gun and chambers a round, then aims the weapon at Pablo and yells. "Move, Ray!" but Ray continues his attack.

Regina comes to and moves to Ray Sr. and puts her hand over the pistol he holds. She gives him a knowing look, and he lowers the gun with tears in his eyes. The sound of a broken bone is heard. Pablo is seen lying on the ground, broken and unable to move. Just as Ray Jr. positions himself to break Pablo's neck, Ray Sr. fires a round into the air. The sound makes Ray stop his attack. "Leave him to the pack of devils he runs with," Sr. demands. Ray Sr. looks at the pistol he holds for a moment and then drops it in a nearby storm drain.

As the family moves away, Pablo tries to get up. Regina puts him down with a final kick. Ray, Regina, and Ray Sr. walk to the main street and blend with the parade. A police car passes them as it moves slowly through the crowd, then turns down the side street where Pablo lies. Minutes later, ELJefearrives in a black sedan and speaks to Pablo. "Look at you—all broken up." "You know what happens when you fail to deliver." Pablo knows. He closes his eyes and waits."The Bosssignals Pablo’s execution.

Three months later Ray returns to the ring with Regina and his father by his side. The action is nonstop, with each fighter getting in telling blows. As Ray falls behind, he looks to his corner for encouragement. Ray takes his father's advice and begins to box his opponent. An uppercut throws his opponent off balance. For a moment, it looks like the strategy will win Ray the fight. However, Ray's opponent adjusts and comes back with a new offense.

It's not looking good for Ray, but when his opponent makes a misstep, Ray seizes the opportunity and knocks him to the mat. Ray'sopponent is dazed and confused but shakes it off. When he starts to get up, his manager gives him a sign, and he collapses. As he is counted out, Ray Sr. registers a look as if to say, "Something isn't quite right?" However, his suspicion is short-lived as Ray's victory is celebrated. Regina and Ray Sr. rush to the middle of the ring and embrace Ray. Ray kisses Reginaas Ray Sr. looks on and smiles. Ray and Regina exit the arena. The fans are held back by security. The crowd chants. CUDA, CUDA, CUDA! Regina and Ray kiss as the crowd continues to cheer for their hometown hero.

From the owner's box, unseen by Ray, the head of the Carteldials his cell phone. A guard hands the ringing telephone to Angel in his cell. "It's for you," the guard smugly says. The voice on the other end of the call speaks slowly and distinctly as Angel takes the phone, "Sometimes you have to handle things yourself." Angel knows the voice and what is about to happen, but he still asks, "El Jefe?" The faceless voice on the phone then states matter-of-factly, "You know what happens when you fail to deliver." With no way out, all Angel can do is utter a futile plea, "No!" The rest of the sentence is cut short as the phone explodes. Engulfing the cell in flames. In the arena still ringing with shouts of “CUDA” El Jefe smiles as he looks forward to managing Ray's career because, after all, "Once a Diablo, always a Diablo."