One of the themes that plays a critical role in the story is the connected themes of religion and corruption. There is religious symbolism in the story, Lucynell is referred to an an angel, Shiftlet cannot see this aspect about his wife, but all the other people in the diner can see that she is holy.
Mrs. Crater wants Shiftlet in her home so that he can fix broken things, she bargains with him and offers her daughter, indicating that people are less important than things. The mother does not seem to find it wrong to offer her mute daughter to an odd stranger.
The car seems to have more value in the story than Lucynell. And finally when Shiftlet leaves Lucynell at the diner, it is the final act of corruption. He takes the car and leaves his wife who resembles an angel. He abandons his salvation, Lucynell, only to grasp the material and continue wandering looking for meaning.