A melancholy figure, Carter is a quiet contemplative dreamer with a sensitive disposition, prone to fainting during times of emotional stress.

He can also be courageous, however, with enough strength of mind and character to face and foil the horrific creatures of the Dreamlands, as described in the stories of the Dream Cycle.

[2] Upon reaching the cemetery, Carter and Warren uncover the crypt by lifting an immense granite slab, revealing a set of stone steps leading downward into the earth.

Shortly thereafter he tells Carter that he has discovered a monstrous unbelievable secret and pleads with his companion to replace the stone and run for his life.

When Carter asks what he has found, his queries are initially met with silence and then by the voice of an unknown entity who informs him that Warren is dead.

"The Unnamable" begins with Carter in conversation with his friend Joel Manton, principal of a New England high school, discussing the supposedly mythical creature that bears the story's name.

After an elaborate odyssey, Carter awakens in his Boston apartment with only a fleeting impression of the dream world he left behind, though he now knows what the lost city actually is.

In an attempt to recover his lost innocence, Carter returns to his childhood home and finds a mysterious silver key, which allows him to enter a cave and magically emerge again in the year 1883 as a child, full of wonder, dreams, and happiness.

"Through the Gates of the Silver Key," written in collaboration with Lovecraft admirer E. Hoffman Price, details Carter's adventures in another dimension where he encounters a more primordial version of himself (implied to be Yog-Sothoth) who explains that Carter—and indeed all beings—are ultimately nothing more than manifestations of a greater being.

Joshi says it would also explain why he was called a "bundle of nerves" in that story, since it took place after his World War I service in which he was nearly killed and might still have post-traumatic stress disorder.

Carter's whereabouts after Cambridge are unclear, but, like his fictional namesake, he may have used the French Foreign Legion as a route into exploring the North African deserts.