Reach the Skip Slope
Before descending, restore the missing rocking chair beside the Chalet fireplace for the Boo. Outside on the Chalet Approach, light the barbecue and carry the burning turkey to melt the ice over the gem painting, then use Dark-Light. Continue through the Airway and Crossroads, activate the E-Gates and move the ice-bound key back to a flame to thaw it. On the Skip Slope, take the first right branch for the key and the later left route behind the rotating wheel for the sapphire. Use the lower E-Gate to repeat the slide if you missed either.
Open the route to the Crystal Quarry
In the Smuggler’s Hideout, remove the ice and clear the ghosts before continuing into the Shaft. Pull the hanging handle during the descent, then ride back up to the opened hatch for another sapphire. Reach Deep Hall and use the Prospecting area’s conveyor to send coal through its E-Gate. Ignite a piece and shoot it at the ice holding the ceiling gem. For the progression key, use a burning piece of wood to clear the bags in the adjacent area, then light coal and shoot the elevated ice. Avoid carrying an unlit rock to a target that specifically needs heat.
Capture the strengthened ghosts
Enter the Crystal Quarry and look into the crystal to trigger the encounter. The strengthened ghosts have more health than the ordinary versions, but the basic method is unchanged: stun, vacuum, pull against their movement and use Power Surges. Capture the first ghost, then the pair that follows. Do not stand between both while charging a flash. Clear the full encounter to finish the mission and expose why the mine’s ghosts have become more dangerous.
Collectible checklist
Secret Mine gems — #6 Chalet Approach, #7 Prospector’s Crossing, #8 Skip Slope, #9 Shaft, #10 Deep Hall
Boo checklist — Chalet: Restore the rocking chair beside the fireplace.