Satoshi who is anticipating his next Gym Battle has returned to the Mio City Gym to challenge gym Leader Tougan to a battle. He arrived to find that Tougan and his son Hyouta are on the battlefield arguing.

Satoshi recognized Hyouta from his earlier Gym battle and Hyouta quickly introduces him. Satoshi and friends quickly find out that there is some animosity between father and son. Tougan takes the group to another part of the gym to check out his collection of fossils. Hyouta and Tougan get into an argument on who's Pokemon is stronger, Rampard or Trideps.

Hyouta and Tougan finally agree to have a Pokemon battle to settle who's Pokemon is strongest. Hyouta sends out his Rampard while Tougan sends out his Trideps. The battle commences and Satoshi is impressed once again at Rampard's speed. The Pokemon seem evenly matched but Trideps manages to get the first blow off before sending a Flamethrower the barely misses Rampard.

Meanwhile, the Rocket Gang manages to dig a hole into the fossil collection room. Nyarth explains that the boss would be able to use the fossils.

The battle continues as Rampard counters with a Flamethrower. Before the battle can be concluded, an alarm goes off and the battle is temporary called off. The group goes to find out what has happened.

Tougan runs into his fossil collection room to immediately notice a hole in the floor and his fossils all missing. Satoshi and friends go down the hole and follow it. At the end of the tunnel, they are greeted by Rocket Gang and their digging mecha.

Tougan isn't impressed by the thieves as Hyouta they are Rocket Gang. Hyouta and Tougan send out their Rampard and Trideps to attack Rocket Gang. Nyarth counters their attacks with their new Digging mecha which throws rocks and sand at Rampard.

Rampard manages to knock over the mecha but is unable to destroy it. Pikachu attacks it with Thunderbolt but is unable to damage it. Realizing that they might be a bit outnumbered, Rocket Gang decides its time to leave. Rampard and Trideps attack the mecha leaving it damaged enough for Pikachu to finish it off finally.

Rocket Gang blasts off as the mecha is destroyed, dropping all the fossils they stole on the ground. The Himanuts leaf fossil is recovered as Hyouta and Tougan recall the past events of a young Hyouta finding the fossil.

Having reconciled their differences, Tougan agrees to have a Gym Battle with Satoshi.