When the mission begins, Harry will appear above you and throw a Pumpkin Bomb. Dodge it if you possible or wait until he hovers to one of the end of the screen, then use the time to collect health power-ups if you were hit. If you were not hit, swing towards him and slide the stylus towards him to hit him in the air. After hitting him, swing across him and stop. He will throw the Pumpkin Bomb again, so repeat this process until his health reaches zero.