Both fighters make it to SPARTA - the winner-takes-all MMA tournament. Tommy is first to fight. No one is sure what to make of him since he declined to give any interviews or give the press any background info, and doesn't even enter the ring to a theme tune. When the bell rings he sizes his opponent up a little, then Tommy soon enough floors him with one punch. Knowing the other fighter is KO'd, Tommy smacks the gate open and leaves to cheers from the crowd.
Next up is Brendan. He's nervous in the changing room, and is a huge underdog against the fighter known as 'Midnight'. He walks out to Beethoven, and even the commentators feel sorry for him. His opponent tries his best to get a submission in the first round, but Brendan manages to hang out and just makes it to the end of the bell before he blacks out. The second round doesn't get much better, but Brendan is like Homer Simpson that time he took on Mike Tyson - he just takes a beating, tiring out the other fighter. He barely makes it to the last round, but this time he senses that he can win - and needs a KO or submission to take the fight. Using his old wrestling ability he turns the tables on 'Midnight' and against all odds gets the submission.
The fighters must fight a second time that night. Tommy returns, fresh as a daisy, and this time lunges at his opponent, taking him out with the first punch. He doesn't hang around and is straight out the gate again. The fans love it.
Meanwhile Brendan isn't feeling too hot and is soon enough losing his next fight - until he gets back to his wrestling background and traps his opponent in a hold ... again forcing a tap-out.
In a scene that will make it clear who we are meant to cheer for, Tommy plays the slots when his old man approaches, again trying to just be friendly and make up for the past. Tommy is vicious and mean to his dad, turning him away with a harsh choice of words.
Next morning Tommy is woken up by his drunken father, who turned to the mini-bar after being rejected by his son. Feeling remorse, Tommy comforts him, although with a strange satisfaction that he was right all along and knew he would turn back to the booze at some time.
Tommy prepares for the fight that night alone - the last 2 rounds of Sparta. Meanwhile footage has leaked about Tommy - that he is a war hero who pulled the door off a tank to save his comrades. As he enters the arena a whole troop of marines have bought a section of seats and sing one of the brothers-in-arms songs in support. Tommy acknowledges them before getting into the ring to face "Mad Dog" - who wants revenge for the beating he took before.
Tommy doesn't waste any time again. He side-swipes Mad Dog's attack, then clothes-lines him onto the canvas before pinning him down and just laying punch after punch into his opponent's head. The trainers scream for him to get off, as the referee tries to pull him away. The twisted boy gets up and again leaves immediately, with the marines cheering him on, booking his place in the final.
Brendan is up next in the other semi - against Koba (Kurt Angle!!) the Russian champion. Tess has taken a seat ringside to spur him on. Brendan again takes a pounding. Meanwhile all his school have met at a drive-in movie park to watch the fight on the big screen, but it's tough viewing.
It needs a few words from Frank to focus his man - that if he doesn't fight now, he'll lose his home. Brendan takes the fight to Koba with kicks and punches, locking him in holds and breaking out of Koba's grip - until the two men wrestle and each think they have the other. Brendan has Koba's foot in a painful hold. He pulls with all his strength, until finally the big man taps out. He's in the final.
In the locker room the news is announced that Tommy is wanted by the army for going AWOL and will be arrested after the fight ... and with more breaking news that both men in the final are in fact brothers.
In the ring Brendan tries to talk to Tommy, but he isn't having it. With pure rage in his eyes Tommy goes for his brother giving it everything he's got. He even gets in a few cheap shots after the bell. The second round is just as brutal as the first. Again it's up to Frank to get his fighter moving, by telling him that tonight Tommy is not his brother, but an obstacle. In the third round Brendan traps Tommy in a good hold, but Tommy doesn't give in and instead tries to elbow his brother to break out. In desperation Brendan breaks his brother's arm.
Full of remorse he is about to call the referee over to break the fight. Tommy is in excrutiating pain, but doesn't let his brother see it. It's not a fair fight. Brendan begs his brother to give up. Frank yells for Brendan to finish it. He roundhouse kicks Tommy in the head, then pins him down and pulls a final hold, exerting more pressure on his brother's arms.
Tommy won't give in. Brendan screams to his brother that he loves him, almost in tears. Tommy finally hears this, and taps out. Brendan wins - and has won the money to turn his life around. Brendan follows his brother's example and turns away from the cameras, instead helping his brother back out the arena. Paddy watches on, with what looks like a tear, before for some reason he loses interest and leaves, which ruins the ending a little.
The final scene has the brothers staggering out to the changing rooms, arms locked around and supporting each other.