How did IT die?

 is the first in a
series
of five books by , referred to as the "Time Quintet."

In

the book, Meg Murry, her younger brother Charles Wallace, and her classmate Calvin go on
a
journey to save Mr. Murry, a brilliant scientist and father of the Murry
children. He is on
another planet called Camazotz, where a large, evil,
disembodied brain referred to as IT is
holding him captive and controlling
the minds of everyone on the planet. Charles Wallace at
first tries to defeat
IT with his extraordinary intelligence, but IT takes him instead,
controlling
his body and mind. Meg eventually realizes that hatred and anger make IT
stronger
and that only love will help her save her brother. She uses her love
for Charles Wallace to set
him free from IT's control. I do not believe IT
actually dies in the
book.