One of the themes of this book is the contrast between thinking and more insensate people. Private Williams and Leonora Penderton are likened to animals. For example, Private Williams is described in the following way:

In his eyes, which were a curious blend of amber and brown, there was a mute expression that is found usually in the eyes of animals. (4)

He is almost like an inhuman creature who is only able to relate to animals, such as the horses in the stables. He also has the stealthy quality of an animal and is able to sneak up on Leonora to watch her while she is sleeping. Leonora is an amoral being who has a particular kinship for horses. She is feeble minded and is nearly unable to write or do math, making her seem more like a beast.

In contrast, Alison Langdon and her house servant, Anacleto, are cultured, refined people who speak in measured tones and carry out more "refined" activities, such as painting.

The refined people in the book and those who are portrayed as more beast-like do not know how to relate to each other. For example, Leonora does not get along with her husband, the more refined Captain Weldon Penderton. He cannot understand his wife, who whips him viciously at a party after he has whipped her horse, Firebird. Similarly, Major Langdon, who is more animal-like, does not understand his more refined wife, Alison, and he doesn't understand how to comfort her, as she is desperately unhappy.

A related theme is the unhappiness in human relationships. Alison Langdon and her husband have a loveless marriage in which she has suffered from the loss of her baby. She cuts off her nipples with shears as a result of her acute mental discomfort. Her husband eventually sends her to a mental institution where she later dies.

Weldon Penderton and his wife, Leonora, are also mismatched, and Leonora is having an affair with Major Langdon. Weldon Penderton secretly harbors homosexual yearnings, but he does not acknowledge them. Instead, the couples live in deep unhappiness with each other and are not suited to each other.