Battle For The Underground! (Japanese: 激走！！ バトルサブウェイ！！ （後編） Flat-out Run!! Battle Subway! Part Two) is the 50th and final episode of Pokémon: Black & White.
As the Nimbasa City Subway fight continues, all of the Pokémon from the Pokémon Center, and others owned by Ash and co. are taken by Team Rocket in their own ghost train. Their plan was running perfectly as they set up more ghost train decoys around the inside of the Subway System and made their way above ground to Anville Town. Will they get them back with the help of Ingo and Emmet? Can Pikachu and Axew escape on their own with help from their Pokémon friends as they let them out of their Poke Balls? And why Pikachu looks super furious when he sees Meowth?
Team Rocket is riding the train away with the stolen Pokémon, sending decoy trains one by one. A train passes by the heroes, but Ash sees it is another decoy. Ash thinks they have to check every train, but Cilan knows that is what Team Rocket wants them to do. Dr. Zager flies the helicopter to Team Rocket's train, who report the success. At the train, Pikachu uses Iron Tail on the door, but the attack has no effect. He tries to get out, using Iron Tail on the door, but fails. Meanwhile, the heroes spot a train, but do not know if it is fake or not. Cilan wonders if Team Rocket is above ground, surprising Iris and Ash, for they always thought the trains stayed underground. Cilan calls them geniuses, for they need to find the exit, for it is the entrance where the ghost train came from.
The Subway Bosses are told this and report Team Rocket must've came from Anville Town into the Underground. Cilan explains the town lies near Nimbasa City, for it is the center of a Metro Connoiseur. Axew cries, but Pikachu convinces him they'll get out. Pikachu uses Electro Ball to bring a Pokémon. It is Snivy, who uses Vine Whip to call another. The next one is Excadrill, who uses Metal Claw to free them. Pikachu uses Iron Tail and Axew Dragon Rage on the door, which still stands. Snivy sends Pansage, who uses Bullet Seed, along with Excadrill, who tackles the door, but no effect happens. So, they think for a while and conclude they need Dwebble. Snivy sends Dwebble, who melts the door by spitting acid.
Ash, Cilan and Iris run, but the Subway Bosses Ingo and Emmet arrived on a cart powered by Emmet's Eelektross' Discharge. Dwebble has made a hole in the door. Mewoth goes to check and sees the hole. Pikachu is very angry at Meowth's betrayal, who replies they will soon be delivered to the boss. Pikachu uses Thunderbolt, but Meowth closes the door. Meowth reports to Jessie and James what happened, who they tell him to do something while they move towards Anville Town. Snivy sends Roggenrolla and Tepig as well. All Pokémon attack the cart connection point, which makes them separated from Team Rocket's cart. Snivy uses Vine Whip, pulling the switching point, which causes them to be separated from Team Rocket. However, Team Rocket goes back and chases the cart down. Meanwhile, the heroes are out of the subway.
Dr. Zager goes after the train, intending to lift it up. The Pokémon attack the helicopter, but it is too sturdy to be damaged. The heroes catch up with Team Rocket's train, so Eelektross speeds up. The heroes decide to get onto the train to save their Pokémon. The Bosses see the kids want to protect the Pokémon as much as they want to protect the Underground. Ingo sends Chandelure, who uses Psychic to transport the heroes onto the train cart. So, Roggenrolla's Flash Cannon, Tepig's Ember and Axew's Dragon Rage speeds up the cart. Dr. Zager goes after them, but Pansage uses Bullet Seed on the track switch, changing the cart's direction. However, Dr. Zager is still going after them, so Snivy uses Leaf Storm to slow the helicopter down and Pikachu uses Electro Ball to destroy the helicopter's cart hook. Team Rocket chases the twerps, so Axew, Roggenrolla and Tepig use Dragon Rage, Flash Cannon and Ember to accelerate, while Tepig learns Flamethrower in the process.
Chandelure uses Will O' Wisp on Team Rocket's train, so Team Rocket prepares their jetpacks. Pikachu is still angry for Meowth's betrayal, but Ash tells him to cool down and thanks Meowth for a good time on their joruney to Nimbasa City. Meowth cannot believe the twerpishness, considering Ash as a fool for such a statement. Team Rocket promises to Pikachu they will capture him one day. Pikachu goes to use Thunderbolt, but the train explodes. Dr. Zager goes away with Team Rocket. Pikachu is still furious, but Ash calms him down. Cilan admits Team Rocket made a great plan, while Iris wonders what would've happened if she caught Meowth.
At Anville Town, Cilan is happy to see more trains. The Subway Bosses report they gave the stolen Pokémon back at the Pokémon Center. Iris reminds Ash he can finally go to challenge the Gym Leader. Ingo and Emmet wish Ash luck, for Elesa is a strong opponent.
Who's that Pokémon?: Eelektross (US).
Cilan's Dwebble used Acid to melt the door, though Dwebble cannot learn this move.