The Worker in between the two buildings will give you a Rocky Helmet. A Pokemon that uses a physical attack against your Pokemon with Rocky Helmet will be dealt damage equal to 1/8 of their total HP. There is a Youngster to the east.
Head back to the beginning of the area and head south. The trash can by the vending machine holds a hidden PP Up. It will increase the PP of one move. Walk east through the grass to find an Ether. Continue through the grass to find a Worker to battle.
East of Worker Eddie is a Protein in the thick grass. A Protein increases the Attack stat of a Pokemon. Head back west toward the vending machine and then head south. As you pass the Worker, Cheren will appear. If you walk through the grass west of the Cold Storage building, you can find a Heart Scale. There are going to be Ice-type Pokemon in the Cold Storage so you may want to have a Fire or Fighting Pokemon handy. Enter the building and Cheren will follow.
Go up the stairs near the worker to the west to find a Net Ball. Go back down the stairs and you will find a floor covered in ice. Anybody who has played a Pokemon game before knows how this works. The first step you take on the ice slides you in the direction you were walking until you hit an object. If you walk up on the very left square of ice, you will slide into a wall of ice. Then press right and you will slide to the opposite side. Press down and you will slide into TM 55 Scald. It is a Water move that can burn which is a pretty interesting combination. Go back to the start of the ice and walk up on any other square and then walk right to battle a Worker.
There is a Hyper Potion to the northeast of Worker Ryan. Try to enter the open crate to the west and Cheren will appear. He will ask if anybody is inside. Say yes. Now is a good time to save if you haven't in a while. Walk inside the crate when you're ready.
Zinzolin, one of the seven Plasma Sages, is inside with eight Plasma Grunts huddled around him for warmth. After some talking, walk straight and fight the first grunt, followed by the three grunts to the right.
Clay will barge in after you've defeated the last Plasma Grunt. Clay's Workers will take the Plasma members away and he will tell you to come challenge him at the Driftveil City Gym. After Cheren leaves, pick up the NeverMeltIce in the northwest corner of the room. It boosts Ice moves by 20%. There is nothing left to do here now so go back to Driftveil and head to the gym in the northeast part of the city.