Outside the Driftveil Gym, Black stands with Nite, Musha and Tula, and wonders when exactly he would be able to challenge the Gymleader, Clay. Earlier, on the Driftveil Drawbridge, he has requested a Gym challenge from Clay, but the man turned him promptly because he was in a bad mood. When Black asked when he could have his battle, the man yelled at him and shouted that he would have to wait until his mood got better.

Recalling how hostile the Driftveil Gymleader was, Black drops his shoulders in despair and knows that it definitely has something to do with him calling the man a rubbish Gymleader when he was tricked by Zorua. He peeks into the window of the Gym, and sees that Clay has assembled his Workers in the lobby. However, he could hear the man yelling at the crew for being too slow, and realizes that he is still in a bad mood. He relents that he should practice on his own for now, perhaps work to train up his newly captured Tirtouga, and turns to walk away.

Inside the Gym, Clay demands a report from the mining team, and the Worker in charge gingerly informs him of their working progress. Some Workers standing at the back start to gossip how Clay seems to be constantly furious lately, and wonder if it is related to the recent incident of mischief at the Driftveil Drawbridge or the delayed construction work on Route 4. However, they believe that it has actually more to do with the expanding underground railway system across the entire Unova region, which development will surely affect the mining business.

Clay overhears his Workers' gossips, and hollers furiously that they should learn to keep their mouth shut during an assembly. He asks the four Workers assigned to Twist Mountain, Felix, Rich, Sterling and Don, to get back to work right away since their reporting is done, and the four men immediately hurry off before the man's rage further escalates. The Driftveil Gymleader scoffs to himself that he is hardly bothered by trivial things like that, and his mind drifts back to the issue that is really troubling him, the mysterious black coloured orb-like artifact which he uncovered from the Desert Resort.

He then remembers how he is supposed to test whether the boy named Black is worthy of asking assistance from, and turns to one of his Workers, Heath, telling him to get the boy to him. Heath wishes to know what he should say, and Clay barks that he asks too much and all he needs to do is tell the boy that a battle is waiting for him. Terrified, the Worker immediately scrambles to his feet, and rushes out of the Driftveil Gym.

Out on the eastern seashore of Driftveil, Black yelps out in pain as his Tirtouga's Pokeball smacks at his hand and bounces off. He bends down to pick up the fallen Pokeball, and wishes that the sea turtle wouldn't turn moody on him too. He remarks that they should try to get acquainted with each other, and pops it out from the Pokeball to test out its strength. He raises his arm to command a Brine and Aqua Jet, but Tirtouga ignores the orders and simply turns away, causing him to drop his shoulders in dismay. He then notices that Tirtouga is even trying to swim back into the sea, and hurriedly chases it back.

At that moment, Worker Heath arrives at the scene, and wants to know if he is Black. He tells the boy that he is wanted by Clay, and informs him word by word that a battle is waiting for him. Black beams at the news, and immediately starts dashing off to the Driftveil Gym, grateful that Clay's mood has finally gotten better. However, Heath reveals that the reverse is true, that the King of Mines is at his worst temper today, and Black sweatdrops at the remark.

Black soon makes it to the Driftveil Gym, and thinks to himself that he must give his best to win this match since it was so hard to get, especially when it is drawing closer to the commencement date of the League tournament. He steps onto the platform in the middle of the room which slowly moves downwards, and takes him to a floor where more platforms are present, each with a set of switches for going up or down. Black recalls from his research that challengers must solve the elevator maze to get to Clay at the lowest floor, and tries his luck at the adjacent platform, which he presses the 'down' button. To his surprise, he has chosen the right platform at his first attempt, and feels himself quickly plummeting downwards to the Gym's basement.

As the platform comes to a stop, Black steps off from it, and finds it surprisingly easy to solve the maze. His words are overheard by Clay, who is waiting for him at the Gymleader's stand, and the man snickers that the boy really has a habit of being rude. Black bolts in horror that he has unintentionally angered the Driftveil Gymleader again, and the man says if he finds the pre-battle maze challenge easy, he should pray for his luck in defeating him, because it will be a hard battle and one will be extremely lucky to obtain the Quake Badge from him. Clay tells Black to be thankful that he will choose to forget all his rude comments, and give him a fair battle.

With that, the man calls forward his Krokorok, and orders a Sand Tomb. Gusts of sand quickly blast towards Black and his Tirtouga, and the sea turtle gets ticked off by the unexpected damage. It jumps out of Black's arms, and unleashes of blast of water on Krokorok, which sends it tumbling backwards onto the floor. Clay is slightly astonished at the power of the attack, and believes that it must be the trump card Black plans to use for his Gym challenge. However, he notices that it wasn't exactly following a trainer command, and Black admits with an embarrassed look that Tirtouga indeed simply retaliated out of its natural instincts. He explains that he has only recently caught this Pokemon, they haven't really worked together in a battle yet.

Clay mocks that Black sure is arrogant to bring such a Pokemon to challenge him, but Black clarifies that he didn't make the decision out of arrogance. Rather, he believes that it was fate that he encountered a Pokemon who excels in water attacks right before he is about to face an expert in ground types. Clay laughs at the boy's words, and remarks that the Tirtouga he has is actually a very rare and powerful species. Upon evolution, it will become the prototurtle Pokemon Carracosta, and Black, upon hearing the fact, decides to nickname it Costa. He hopes that it can help him out in this battle with its powerful water jet attacks, but despite his enthusiasm, the sea turtle still turns away with an indifferent look, and Black once again sulks in despair.

Clay laughs that he shall show Black how powerful water jet attacks work, and sends out his Palpitoad to deliver a Hydro Pump, which hits Costa forcefully. The blue toad follows with a Hyper Voice, and causes Black to hold in ears in pain while Costa folds itself into a defensive pose to block out the sound waves. Clay states that although it is usually an act of confidence to face one's back to the opponent during a match, Tirtouga's current posture looks more like it is surrendering.

The Driftveil Gymleader switches in Excadrill to continue attacking, and the steel mole folds itself into a driller to start boring into Costa's shell. The Tirtouga stays motionless at the assault, and Clay laughs that it certainly seems to lack a battling will.

Black grunts in frustration, and wonders what he should do, but soon notices something interesting. Excadrill soon tires itself out from the drilling and tumbles off Costa, but Costa itself is genuinely unharmed by the attack and is even dozing off. Black exclaims that it is amazing, and Clay grins that he never doubted his Excadrill's strength. However, Black is clearly not referring to the subterrene Pokemon, and says he isn't talking about it, which makes Clay think he is rude again. Black stutters that Excadrill is marvelous as well, but he is more fascinated that Costa's shell fended off all the damages. He states that when it uses Withdraw, its defense is so much that it is basically an impermeable solid wall. He believes that having impeccable defense is also one kind of battle tactics, and merrily picks up Costa's fore-fins, marveling at its greatness and feeling thankful for having encountered it.

Black's direct appraisal causes the sea turtle to feel embarrassed, and it blushes as it turns its head away. Black gives it a friendly smack on the shell, telling it not to be shy, and Clay watches in amusement as he sees how the boy interacts with his Pokemon. He is impressed how he nurtures the relationship with his team member even during a match, how he remains optimistic even in unfavorable situations, and thinks that he is indeed an interesting lad just like Lenora told him.

Meanwhile, at the Striaton Gym, Cilan, Cress and Chili each takes a sip of freshly made tea from their cups, and decide that it is time. They get Pansage, Panpour and Pansear ready, and set out on their way to the Nacrene Museum.

At the Nacrene Museum, Patrat and Stoutland take another good look around, and return to Lenora, reporting that they did not spot anything unusual. The Nacrene Gymleader is slightly surprised that not a single suspicious trace of the enemy could be found, even though she feels quite curtain that it is just under their noses. On a tree behind her, a spy camera shaped like a Roggenrola opens up a pair of wings like a Woobat, and flies off with a pack of real Woobats towards the sunset. Lenora catches a glimpse of it at the corner of her eye, and watches it disappear from sight in silence.

Back at the Driftveil Gym, Black is astonished to hear that the Gymleaders he has fought so far have been talking about him. Clay says the others spoke of him as a hot-headed guy who isn't afraid of anything, and Black blushes at the remark. Clay believes that as an impulsive guy, Black will not be too startled by what he is about to tell him, and Black is curious as to what the man is talking about.

The Driftveil Gymleader remarks that he is nicknamed the King of Mines. He excavates minerals as a living, and it is mainly for the purpose of making money. To be frank, he isn't too crazy about things like affection to the old world, but despite being someone with a practical mind like that, he still encountered an item by fate, which captivated him and forced him to connect to the past.

Black still doesn't get what Clay is saying, and the man reveals that during an excavation at the Desert Resort, he and his team came across an artifact which possessed great energy. The item was shaped like a stone and was buried in a very ancient layer underground. Upon obtaining the stone, Clay felt right away that it was outside his capacity to control it, and he couldn't wait to lay off his hands from it. Due to a hunch that the item was related to the old world, he contacted his good friend, Lenora of the Nacrene Museum, who has a passion for ancient relics and hidden treasures. Lenora took the item back to her Museum for investigations, and eventually learnt that it was called the Dark Stone.

Clay points to Costa, and wonders if the boy knows that his Tirtouga is an ancient Pokemon who swam in the seas 100 million years ago. He believes that it must have borne witness to the entity transforming into the Dark Stone, and Black gets even more confused after hearing that. Clay wonders if Black has heard about the legend of the founding of Unova, and says in the myth, there was a Pokemon which was called the black lightning dragon.

Black bolts in recollection that one of Team Plasma's Sages said something similar at Castelia City, and Clay reveals that this black dragon is named Zekrom. He state that after Lenora did extensive research from literature and ancient documents, she eventually discovered that the Dark Stone is in fact the legendary black dragon Zekrom itself…