Captain Toad finds himself on the walk up to Boo Mansion. It's a maze of doors. Near the front door is a Goomba. The plant to the right has the first gem. Some of the doors are part of touchstones. Move the touchstone above the front door, then go through the front door. Move the touchstone back, then cross the bridge, which drops partially to become a ramp. In the backyard, there are four doors. Move the upper right one in front of the second gem and go through the lower left door to reach it. Move the upper left one back, then go through the lower right door to land on the lower left door's touchstone. This will allow you to go over the fence. Boos will appear here. You can use your flashlight to defeat them. Move the top door's touchstone, then go through the door at ground level when the stack of Goombas with the third gem are near the wall. You'll drop down on them to defeat them and get the gem. If you walk around to the front of the house and go through the door at ground level, you can get a Mushroom from a plant. Move the touchstone door back, then go through the same door. You'll end up in a corridor to another door. The door will take you to the roof, where the Star is. Once you drop down from the door, two Big Boos will appear. Go through the door in the corner once the Big Boos approach you a little. The door will take you to a door behind them. Run to get the Star.
Special Challenge: Clear in four touches.
To do this, you'll move the first touchstone (over the front door) twice. Next, touch the upper left and lower left doors when you're in the area with the second gem. Everything is in place from there.