After the Joker attempts to kill Harley, she meets Poison Ivy, who saves her. Coming to feel a kinship with Harley, Ivy offers to help Harley take her revenge on both Batman and the Joker, giving Quinn a treatment that immunizes her to various assorted toxins and Ivy's own poisonous touch. It also dramatically enhances Harley's strength and speed, which gives Harley an edge on Batman and the Joker.