Cosmic evil is connected with evil on a cellular level, and the children along with some new friends go within Charles Wallace in order to save his mitochondria (and the fictive entities living within them, the farandolae) from the un-namers—the Echthroi (the Ancient Greek word for "enemies"). The Echthroi are powerful, evil creatures whose desire is to X (i.e. extinguish, unname) creation. Author Calvin Miller writes that the Echthroi are "demonic spirits" that "are always stalking good, making the whole sick, the entire partial, the holy eroded by the contaminated."[3] The Echthroi reappear in A Swiftly Tilting Planet, trying to prevent Charles Wallace from reaching key moments in history in a bid to save the world from nuclear destruction.
Space and time hold little meaning within the Time Quintet series. In several instances, we find Meg and other characters frustrated with their new friends and confused about these concepts. However, according to the mythical creatures that are introduced, these concepts are limiting and unimportant. This is the key concept to understanding why Charles' sickness could be so important. His sickness, the ailment of his mitochondria, is just as important as the fate of a planet elsewhere in the universe because each part of creation, great or small, is important.
Like all of L'Engle's books, the power of love is again a force to be reckoned with as it helps save several characters—not just Charles Wallace but also Meg and a farandola named Sporos. Meg learns to see beyond superficial impressions, and appreciate and embrace inner beauty and strength. Much of the communication between characters in this book involves a process called "kything". This process is similar to telepathy and empathic abilities combined. Meg also learns that she is a Namer. Namers work in the universe to love and Name parts of Creation, and help them to be themselves. This is the exact opposite of what Echthroi do in their Xing or unNaming.
The premise of Naming and counting is inspired by passages in the Gospels of Matthew and Luke which say that God has numbered every hair on our heads and that God is aware of every sparrow that falls. In her book The Rock That Is Higher, L'Engle mentions this concept, and the interdependency that is at the heart of A Wind in the Door:
The secrets of the atom are not unlike Pandora's box, and what we must look for is not the destructive power but the vision of interrelatedness that is desperately needed on this fragmented planet. We are indeed part of a universe. We belong to each other; the fall of every sparrow is noted, every tear we shed is collected in the Creator's bottle.
— Madeleine L'Engle, The Rock That is Higher: Story as Truth, ISBN 0-87788-726-8
The title is based on a quote from Le Morte d'Arthur.
