This stone looked nearly the same, but it wasn't. It was the Substitution Stone, which worked just like the normal stone, except that after the wisher stated his or her wish, one of the words of the wish was substituted by another word, but a word that would still make some sense.
For example, if Zoe said "I wish I was drinking a glass of milk," the stone would then grant it in a number of other random ways, like "I wish Athena was drinking a glass of milk," or "I wish I was throwing a glass of milk," or "I wish I was drinking a glass of juice." Of course, all of these examples are fairly harmless, but the stone could do a lot worse (like instead of juice, the stone could replace the word "milk" with any kind of liquid, like blood or gasoline or even something disgusting like urine).
Zoe walked towards the spot where she usually met up with her friends before school. And as she approached Athena, she took out the stone, completely unaware that it wasn't the same stone she inherited from her grandfather.
