In the vibrant and chaotic city of Gotham, Harley Quinn finds herself at a turning point after breaking up with the Joker. Free from the chains of her toxic relationship, she decides to take control of her life, but soon discovers that being a single woman in a criminal world is not as easy as it seems. With her unmistakable style, Harley begins to enjoy her newfound freedom, only to face a new danger when the feared organized crime of the city realizes she no longer has the protection of the Joker.
When the young Cassandra Cain, a small-time thief with surprising skills, steals a valuable diamond belonging to the ruthless Black Mask, Harley sees an opportunity to reclaim her status in Gotham. However, Black Mask, played by the charismatic Ewan McGregor, is hot on her trail and will stop at nothing to recover what belongs to his collection.
To survive, Harley teams up with a group of unusual allies, including the fierce Huntress, the warrior Renee Montoya, and the fun, empowered Black Canary. Together, these strong and diverse women must set aside their differences and learn to work as a team. Amid explosive fights and tons of dark humor, they embark on a mission to protect Cassandra and prove that sometimes, true strength lies in friendship.