Toadette finds herself in a two-story building that is dark, but partially lit by torches. There are Shy Guys patrolling all over the place. Be careful to not be spotted by them. You can kill them, as long as they don't see you. They'll notice you if your headlamp is on, so turn it off by pressing (Y). Sneak past the first Shy Guy and go into the dark hallway. Rotate the camera around and you'll see a small room to the right. Sneak past the Shy Guy here and climb up the ladder for the first gem. Continue to the end of the dark hallway, where you'll find yet another Shy Guy. Sneak past it and climb the ladder. There's a Fire Piranha at the top of the ladder. Lure it into breathing fire at the corner in front of it. This will make a torch light up and the second gem will appear on a set of stairs. Around the corner are two Shy Guys patrolling the area. Follow behind one of them until you reach a doorway. Go through the doorway to find the Star and another doorway. That doorway leads to a plant with the key. Grab the key and use it to unlock the door where the Shy Guys are patrolling outside of the room with the Star. Go down the ladder and through the purple pipe. You'll find three Fire Piranhas and six plants here. The plants have coins, turnips, a Mushroom and the third gem. You can lure the Fire Piranhas to breathe fire on each other so you can pick the plants in peace. Once you have the gem, return to the room with the Star.
Special Challenge: Slip past all the Shy Guys.