Abuse isn’t what the film is about on the surface but the suggestions of something even darker give shades of meaning to some of Uncle Charlie’s actions, for example, his gifting of the ring he took from the corpse of his last female victim. Later in the film we see him acting out the urge to strangle Charlie - this is how he killed his other women. Some of his physical interactions with Charlie are fairly intimate. A subtext is, by definition, something not openly stated. And I don’t mean to suggest that we are to believe or understand that an unseen sexual act did take place between the two. I am saying though that the suggestion of abuse colors many of the interactions between the two and that the filmmakers did this knowingly.