At its core, this difficult text is a story of love, loss, and revenge. If your assignment is fairly open as far as topics go, I encourage you to brainstorm ideas revolving around one or more of the above subjects and to come up with a theme statement. In order to accomplish this, you must ask, "Through events, details, and techniques used in this play, what is the author trying to say about one (or more) of the subjects above? What message is he trying to get across?"
In order to answer this question, you must look specifically at the events, details, and techniques used in the play and how they work to create the author's message. Brainstorm a list of ideas/examples, then organize your examples into logical categories. Once you come up with a theme statement (which can be used as the thesis for your essay), prove it by providing examples in an organized fashion (which are your sub-topics).
To help you get started with some "good points" to consider, I offer the following. Consider...
- the idea of teen-aged mothers as two of the main characters.
- the use of an evil "fairy" character who is able to change forms in order to seduce, manipulate, and entrap.
- the use of language: The Skriker's prose as compared to the modern English dialogue of the two girls.
- the elements of horror: psychosis, possession, magic, and the supernatural.
Additional information about putting your ideas together in an essay can be found in the second link below.