"There are two kinds of women: day women and night women." The juxtaposition examining the qualities of night women and day women. The time of day the woman in the story exists in is not arbitrary but influenced by the care she devotes towards her son. Her character develops over the span of her dislike for the time she has to spend at night,  to the ambivalent resignation "The night is the time I dread most in my life. Yet if I am to live, I must depend on it." This transcends the simple concept of time and really is an examination of her means of survival as she deceives her son.
     Throughout the nightly "grind" she's hyper aware of her son. She never alludes to performance anxiety but I imagine it's a persistent issue for her. "Somehow in the night, he always calls me in whispers. I hear the buzz of his transistor radio. It is shaped like a can of cola. One of my suitors gave it to to him to plug into his ears so he can stay asleep while Mommy works." Demonstrates her auditory attention directing towards her son. And "The stars slowly slip away form the hole in the roof as the doctor sinks deeper and deeper beneath my body. He throbs and pants. I cover his mouth to keep him from screaming." shows the actions she takes during coitus to maintain her sons ignorance. What further actions would she be willing to take?
     Whatever the outcome, there doesn't appear to be any end in sight. She's internally concocted fabrications for the boy, preparing to tell him that any one of her nightly clients is the poor kids father, should he discover them. It's a twisted amalgamation of Russian roulette and Schrödinger's Cat in which the kid's image of his father(who he was told died) will be determined by whether or not he peaks behind the curtain on any given night. Pick your poison.