In her Newbery Medal acceptance speech, MacLachlan asserts that complex levels of meaning exist "behind each word or between words" and that the unspoken words often create the most powerful aspects of a book. Indeed, the title character of Sarah, Plain and Tall is a quiet woman. She shares her time, her interests, and her love, but she keeps her thoughts to herself.

Throughout the novel Anna must guess at Sarah's real intentions. When Sarah learns to repair the roof, she appears to want to stay. On the other hand, when she learns to drive a horse and buggy by herself, it seems that she might leave.

Sarah loved living near the great, wide-open sea, and she learns to love the similarly wide-open spaces of the prairie. The images of windswept fields and a prairie that "reached out and touched the places where the sky came...