What is the fine-grained topic of the following text: Harley unites with Scarecrow with plans to destroy Batman, who she still blames for the death of her Mr. J. Grief-stricken and vengeful, Harley brutally reasserted control of the remainder of Joker’s gang and leads them against the bat. Only return the topic.
Harley's alliance with Scarecrow to seek revenge on Batman for Joker's death.