The movie begins with the regular flyby of Pokemon, showing every single one revealed so far. Ash is battling a Kurimugan in an arena with Pikachu. Jessie and James, in their trench coat disguises, can be seen by a yellow car and in a field. The trio head towards a train.

Keldeo is training with Virizion in tall grass. He chases Virizion through it as she coaches him. He attempts to make a sword with his horn and it glows rather dimly before fading. Next he is training with Terrakion who is good spirited and grinning. Keldeo manages to land a kick on its chest. Finally, a lightning storm is brewing and Keldeo and Cobalion are galloping through the trees. Keldeo asks for a battle but Cobalion warns the storm will only worsen. Trees crash and burn and Keldeo puts out the fires with his water hooves. He begs Cobalion to permit his battle against Kyurem, but Cobalion refuses the request, as Keldeo is still unable to use his sword. Later, the four are relaxing by a river. The three discuss Keldeo and his progress, but Cobalion still thinks he is not ready to face Kyurem. Keldeo approached, saying he overheard everything, and he wants to know, what is so important about being able to use the sword? Cobalion tells him to think about it, and Terrakion jokes he is not even so sure himself.

At night, the four are sleeping in the grass, but Keldeo gets up silently and walks off to find Kyurem, deliberately and knowingly disobeying his mentors. He travels to old, rusty and rotting mines placed inside a looming, dark mountain crater. He looks at Freezio circling. He knows this is the place. He calls to Kyurem for a battle. Kyurem looms out of the darkness, stomping slowly forward, and Keldeo claims to be a Sacred Swordsman already. Kyurem then creates a gate of ice, daring Keldeo to cross the gate.

The other Muskedeers have awoken to find Keldeo gone and instantly know their apprentice has gone to Kyurem. Terrakion roars, and Keldeo hears him and knows they are coming. They run as fast as they can.

Keldeo crosses the gate into the icy arena and the battle begins. He does manage to land a kick on Kyurem's chest, but is quickly pummeled and beaten with ice moves and shadow claw-looking moves. The others arrive and are shocked and alarmed to find he has already crossed the gate, locking him into the battle until it is over, and are even more disappointed when they hear Keldeo blatantly lie about already being a Swordsman. Kyurem changes to White Kyurem. Keldeo is petrified with fear, shaking, whimpering and unable to move or defend himself any longer. He is hit hard and his horn is snapped off. Keldeo stares in shock at his broken horn tip, gasping weakly.

Terrakion can't handle watching his small friend being beaten so brutally and rushes to help despite Cobalion's protests. (White) Kyurem is angered at the intrusion and uses what looked like Cross Flare to lock them into a block of ice. Keldeo, too terrified to stand it anymore, runs off as Kyurem angrily growls that this battle is not yet over.

Opening credits!

Ash and the crew are on a train, a few stops from their destination. Zuruggu, Mijumaru, Pikachu, Kibago are goofing off on the train, bothering their trainers, entertaining children, and knocking their trainers around some more. The train stops and Dento dictates to the other two they only have three minutes and they MUST obey him, as he is an Ekiben (train station bento) Sommelier. They rush out and begin to order dozens of Darumaka Bento lunches from the stand. Rushing to get back to the train in time with piles of bento in their arms, there is some chaos with Ash tripping and bento boxes going flying.

Keldeo, weak and stumbling, rolls down the hill and flops onto the top of the train. The train departs, but oops, Zuruggu has been left behind and runs in a panic to catch up. Ash and the others reach out and finally Tsutarja catches him with her vines. Ash hugs him tightly and apologizes, but Pikachu looks up as it hears a weak moan. It jumps onto the roof of the next car and the others follow to find Keldeo, who instantly begins growling angrily and attacking them. They see how weak and scared he is and are surprised when he begins to speak his terror of Kyurem, who he knows he coming.

The train cars begin to freeze as a mist overcomes them and Freezios circle closer. Kyurem jumps onto the train and menaces the trio and Keldeo, who get up and run, Ash helping the limping and injured Pokemon along. They jump into an empty coal car and Kyurem looms over to attack, but is forced to jump off as the train enters a tunnel. Iris recalls hearing about Kyurem from the old woman of her home town. She recalls being told it is a dragon she may not like. She comments she loves all dragons, but seems nervous being told it is a freezing Pokemon. She is told he was born at the same time as Reshiram and Zekrom and is the strongest dragon in Isshu.

They go to the Pokemon Center and Nurse Joy tells them how surprised she is Kyurem has left his mountain sanctuary and that he rarely does so. She also explains to the trio about the Muskedeers and their legend, how they protect Pokemon and train Keldeo, and Ash is entranced by the story.

When Keldeo is healed he walks with the trio and explains what happened. He explains about the battle, his mentors being trapped, and how he ran away. He explains how one cannot become a Sacred Swordsman until one can defeat Kyurem. He is obviously terrified. Ash begins to taunt him about his fear, angering him into swearing to save his friends. Ash grins and nods, having wanted him to say that, and agrees to help Keldeo.

But, Dento forces them all to sit and have their ekiben first!

The pond near the park they are in becomes frozen as mist swirls around it. Kyurem is coming! He and his Freezio posse have arrived and Kyurem becomes White Kyurem again to attack. As the trio witness his transformation, Iris recalls the old woman explaining to her about Black and White Kyurem, and how Kyurem can harness Reshiram and Zekrom's powers at will. The trio are chased endlessly by the Freezio through the city and are separated. Ash, Keldeo and Pikachu continue to run as White Kyurem pursues them past buildings. Keldeo has Ash hold on tight as Keldeo shoots water from all four hooves, flying around crazily with the water shoots out a window and down to the ground level. Keldeo looks a bit confused about his front hooves having shot water.

They get back with Dento and Iris and run into an old Subway entrance. A few Freezio follow. Dento explains this tunnel hasn't been used in a long time and can't get the locked door open until Keldeo kicks it down. He prepares to kick in the next door too and is grumpy when Iris pushes it open easily as it was not locked. Ash and Keldeo are also both hungry again.

Dento is pleased to show the old station is now a museum for old transportation devices. A plan is hatched off-screen. A blimp from inside the museum is stolen and flies away. Freezios go after it. Iris is flying the blimp and taunts the Freezios when they finally catch up and look in, waving happily with Kibago and saying only they are in there, without Keldeo at all! White Kyurem appears then and cuts her taunting short. He changes directly from White to Black Kyurem and attacks, sending the now frozen blimp spiraling out of control.

Ash, Pikachu and Dento are shown emerging from a train. Off-screen they separate, and the train drives off alone, watched by Freezios.

Ash and Keldeo are walking. Keldeo is amazed as it recalls Iris happily offering to use herself as live bait to lure Kyurem and the Freezios away. He talks of his three mentors, how he admires them, and how he misses them. He recalls how it was explained to him by Virizon that the only thing to fear is fear itself, and how Cobalion told him it is okay to lose as long as you learn something from it.

Back with Dento, he is shown to be powering his train car using Maggyo's electricity. He continues to speed along and Freezios appear and attack. He sends out his Iwapress to hold them off, having it use an attack just as they enter a tunnel. The tunnel is dark and things begin to freeze in a mist. Black Kyurem attacks and Dento waves again happily to show he was also just a decoy. Black Kyurem changes to White and flies off.

Keldeo thinks of Dento's sacrifice as well, then asks Ash why he is helping. Ash answers simply, because they are friends, and it is interesting to be with Keldeo. They arrive at the old mines, where Kyurem has returned to and also reverted to his regular self, and Keldeo cannot move forward suddenly from the terror he feels. He recalls his horn being snapped over, flashing back to the moment, and trembles and whimpers uncontrollably. He suddenly admits to Ash that he lied to Kyurem about being a Sacred Swordsman, and now he will never be forgiven. Ash decides to go on ahead promising to help free the other three. Keldeo tries to follow but is frozen with his own fear, standing still as he shakes and whimpers.

Iris and Dento manage to find one another and head off. Ash, meanwhile, locates the deer and begins to hack away at their ice tomb with a crowbar, and with the help of Pikachu's iron tail, Gantoru and Chaobuu. Kyurem, angered by the intrusion, demands that humans must leave this place, and Ash shouts back arguments at him that he does not care. Kyurem is even more angered and attacks, but the attack is blocked by Keldeo. Ash is ecstatic, saying he knew Keldeo would come, he believed in him and that he would come to them. Dento and Iris also arrive to help free the Deers.

Keldeo admits to Kyurem that he lied, but he did it since he was just so desperate for their battle. Kyurem is nonplussed, stating he knew Keldeo was a liar from the start. He creates the gate and arena from ice once more, daring Keldeo again and demanding they end this. Ash shouts to Keldeo to be more "resolute"! Keldeo flashes back to his friends and mentors. He knows he was never alone, that they are the ones who raised him, and he must not run away!

He changes into Resolute Form.

But Kyurem says his new sword - his blue horn - is still not enough, as they do battle. He becomes Black Kyrem and uses Freeze Bolt, freezing Keldeo's leg to the ground. Ash has Pikachu use Thunderbolt on Black Kyurem but Keldeo knocks it away to stop the interference and frees himself by himself. Finally, with much hacking and melting, the deers are freed. Ash is shocked as they know his name, but they explain they heard it all through the ice, and thank him for supporting Keldeo. Kyurem reverts back to normal form, and the Deers and trio watch, not interfering.

Keldeo remembers the advice of his mentors again: Terrakion's advice to "never take your eyes off the enemy." Virizion's advice to "defeat your fears". Cobalion's advice to "learn from your losses". He is able to get in a hit on Kyurem, and the Deers are proud of him, but still not sure he can use his sword. Kyurem becomes Black Kyurem and uses Freeze Bolt. Keldeo is frozen solid by the attack, and the trio and the Deers are extremely upset by this, until Keldeo manages to break himself entirely free. His horn becomes a sword longer than his own body length -- Secret Sword -- and he attacks Black Kyurem with it, and is able to hit him.

Black Kyurem is pleased and grins as he growls this is what he was waiting for, and NOW this is a real fight! He goes into overdrive and uses Freeze Bolt again, and Keldeo leaps up, blocking the attack from hitting Ash, Dento, Iris, and the three Muskedeers. He is hit hard by the attack and collapses. The dust clears. Black Kyurem steps onto his horn, holding him down on the ground. Keldeo admits his defeat.

Kyurem goes back to his normal form then. He is impressed that Keldeo chose to protect his friends over winning the battle. He compliments Keldeo's sword and says it is good...then he walks off. Cobalion is proud that Keldeo has finally understood the importance of the sword.

After all the damage sustained, the mines suddenly begins to collapse upon themselves. The trio ride the deers to safety -- Dento on Terrakion, Iris on Virizion and Ash on Cobalion -- but Kyurem turns to White Kyurem and easily freezes the collapsing pieces into place. Rather nonplussed by the near disaster, he turns back and tromps off into the darkness alone.

The Deers accept Keldeo as a Sacred Swordsman and Cobalion says the humans may witness Keldeo taking his vow. All four place their swords together and say their vow: "Beyond one, two. Beyond two, three. Beyond three, four. When companions' powers unite as one, true power and true bravery are born!"

The ending credits then show the trio returning the blimp - which they stole - to the museum, the four Sacred Swordsman doing their duty running to protect, and Kyurem stomping around. Jessie, Meowth and James are also shown watching the sun set in their trenchcoat disguises by a yellow car.

Special Thanks to Gin of Sunyshore.com for allowing us to use this summary