What idea does Meg share with Calvin to try to free Charles Wallace from the mind control of IT?

Meg tells
Calvin to use his gift of communication to try to free Charles Wallace from the control of IT.
You can read all about this in chapter 8.

In that chapter, both Meg and
Calvin realize that Charles Wallace is a shadow of himself. Frustrated at their inability to
help him, they each take hold of Charles. However, Charles is now far stronger than either Meg
or Calvin. He...