Instructions
Press the "C" button to switch to Madam Pomfrey, and press the "2" button to select the orange Reducto spell in her collection of spells. Press ̶0;Z̶1; to cast the spell on the locket cabinet in the top-right corner of the room.
Switch back to Hermione, have her stand in front of the cabinet and press ̶0;Z̶1; to have her jump into the cabinet to get a pair of earmuffs. Walk up to the Mandrake crying in the center of the room. Press ̶0;Z̶1; to pick it up.
Walk toward the front of the room with the Mandrake, and stand in front of the glass case to the left of the locked door. The cry of the Mandrake will break the glass, revealing a pink flower ingredient that you need for the potion. Press ̶0;Z̶1; to drop the Mandrake and press ̶0;Z̶1; again to pick up the ingredient. Take it over to the cauldron and drop it in.
Cast the levitation spell to lift the head of the skeleton sitting on the bedside nearest the locked door, and place it on the incomplete skeleton. It will come to life and perform a dance before falling apart. One of the pieces of bone will have a blinking arrow above it. This is one of the potion ingredients. Press the ̶0;Z̶1; button to pick it up. Take it to the cauldron and drop it in.
Walk over to the bed on the left side with the student in green lying on it, and levitate it with the levitation spell. As you do so, pieces of a broken, armored knight will come out from underneath and reassemble in front of you. Once put back together, it will walk over to the locked door and break off the lock. Walk through the now open door.
Cast the levitation spell to lift up the brush to brush away the cobweb that is hanging to the right of the open doorway. A new one will appear, but this time with a red spider in the center. This is the last potion ingredient that you need. Levitate the brush again to brush the cobweb away. The red spider will drop to the ground. Walk up to it and press ̶0;Z̶1; to pick it up.
Head back into the other room and drop the spider into the cauldron. As soon as the potion is complete, a cutscene will play, ending the level.