Triplet Stones: Mikey is 3rd

The stranger walked across the hall to their final victim's bedroom. They laid the third and final wishing stone besides Mikey's pillow, with another anonymous explanatory note. The shadowy figure left Jon's little brother and the house, quickly and without a sound. They were terribly excited at the mayhem this stunt would cause. But who was going to wake up first and find their own magical wishing stone?