Instructions
Approach the Skorupi near the large wooden gate in the Hub. Press the "2" button to speak to the pokemon and have it open the gate for you.
Continue through the gate and confirm that you want to enter the Granite Zone when prompted. Pikachu enters the Granite Zone.
Follow the path to enter the Granite Zone ruins. Approach the Absol against the ruin's east wall and press the "2" button to speak to him.
Agree to participate in its attraction and select the pokemon you want to use to begin the race. Turn the Wii Remote on its side and then shake the Wii Remote up and down to begin running. Press the "2" button to jump over any hurdles. Come in first place to complete the attraction.
Approach the Hoppip guarding the doorway against the ruin's west wall and then press the "2" button to speak to it. With Absol's attraction completed, the pokemon lets you proceed.
Press the "2" button to dash into the switch just beyond the Hoppip. The bridge in front of you turns, letting you cross the chasm.
Run across the bridge and up the ramp leading outdoors. Upon walking outside, a Flygon speaks to you. Approach the Flygon, who reveals that he is guarding the secret door.