Possible Thesis Statements:
* The destructive power of fear and suspicion: The story highlights how fear and suspicion can lead to irrational actions and ultimately destroy relationships.
* The fragility of human connection in the face of isolation and the unknown: The isolation of the woods and the presence of the mysterious "monster" threaten the couple's bond and expose their vulnerabilities.
* The danger of succumbing to primal instincts: The story suggests that even seemingly civilized people can be driven by primal urges in times of fear and uncertainty.
* The importance of communication and understanding: The lack of communication and trust between the husband and wife contribute to the tragic ending.
Ultimately, the reader can choose to interpret the story's "thesis" based on their own understanding and interpretation of the themes and ideas presented.