Louise's hair
Louise's red hair is her physical trait that is most often mentioned in the novel. In her lover's eyes Louise's hair is blazing, it's like a swarm of butterflies or a blanket that could cover them both. The insistence on the description of her hair the color of blood is connected to the portrayal of passionate love towards Louise, portrayal of Louise as a character from the lover's eyes.
Circadian clock
The narrator's circadian clock, when it comes to being in relationship lasts twenty-four weeks, after that the feelings fade but, they hopefully won't fade with Louise. The narrator is afraid and hopes that this thing going on with Louise will last past that period. The narrator wonders what affects the circadian clock-the exposure to light possibly. So how long will it take to be under Louise's light?
Memories
The plot of the novel is a mix between the present with Louise and memories of previous life. Those memories are mostly about the narrator's previous relationships, all of which didn't last long, and most of which were complicated due to them being married women. From those memories we can see that none of the relationships fulfilled the narrator's desire for a passionate and safe love both at once.
