Continue along the first hall without incident then exit to the next room. Before continuing in the second area, a Team Flare Grunt will stop your advance.
Team Flare Grunt (Prize Money: 1,280)
After defeating the TF Grunt, enter the room to the right. The man in the suit will sell you Fresh Water for P300 instead of the usual P200. Get the Zap Plate from one of the cubicles to the right as well. This item boosts the power of Electricity moves of the holder. Leave the room and follow the path north. You have to face another Team Flare member.
Team Flare Grunt (Prize Money: 1,320)
After defeating the grunt, exit through the door and you'll find yourself in the outer walkway. Another TF member will confront you.
Team Flare Grunt (Prize Money: 1,360)
The path to the right will be blocked so you have no choice but to make your way to the left. Another TF grunt will engage you to battle and one more after that battle. Continue along the walkway and you'll encounter more TF members in mandatory battles. This will continue for a few more times as you walk around the walkway.
Team Flare Grunt (Prize Money: 1,280)
Team Flare Grunt (Prize Money: 1,280)
Team Flare Grunt (Prize Money: 1,360)
Team Flare Grunt (Prize Money: 1,320)
Team Flare Grunt (Prize Money: 1,240)
After reaching the other end of the walkway, take the ramp to the left to catch up with this group's leader.
Team Flare Admin (Prize Money: 2,880)
This battle shouldn't take long. Houndoom's fast and hits considerably hard but it's not that tough enough to pose problems with your team.
After defeating the Admin, you'll have a break. You can heal up your pokemon and save your game. Talk to the other Team Flare member to engage her in battle.
Team Flare Aliana (Prize Money: 5,320)
Aliana's Mightyena hits harder than any of the Team Flare pokemon you've encountered so far. It doesn't have any moves that you should be wary about.
After defeating Aliana, she and the Admin will leave. Two familiar faces will arrive too. They will give you Full Restores and heal your pokemon too. After they leave, you have to backtrack all the way back to the room where the hostages are held.
Once there, talk to the construction worker to the left to get TM43 Flame Charge. Talk to the scientist to get a Magnet. This also boosts the power of the item holder's Electric-type moves. Talk to the man selling Fresh Water earlier to discover that he's now selling those for P100 each. Leave the power plant.
Head to the right and the construction worker who's blocking the stairs leading to the northern part of Lumiose City is now out of the way. Go downstairs and you'll see a tall guy mumbling about a flower pokemon that's been given eternal life.
Go south then head to the right. There should be a small path with some boulders you can smash. Examine the space south of the boulder to find a hidden Stardust. Use your Dowsing Machine if you want to know its exact location. At the end of the path lies a Rare Candy. When ready, enter the transition gate to the south.
The guy is still there... Help!!
Thanks!!!! :D