Harley Quinn and Poison Ivy are on the run with the Floronic Man hot on their trail, desperate for Poison Ivy to understand her connection to the Green and join his new Parliament of Flowers. Knowing Gotham City isn’t the safest place for them under the new Bane order, Harley takes a hard left down a rabbit hole to seek sanctuary with a former patient and colleague, Jervis Tetch-a.k.a. the Mad Hatter-but his wonderland home isn’t all that it seems!

In Gotham City, where heinous acts of violence are a daily occurrence, the GCPD relies on Harley Quinn, a young forensic psychiatrist and profiler, to consult on their toughest cases. But Harley is haunted by one unsolved case-the night she discovered her roommate’s body marked with the signature of a notorious serial killer known as The Joker. Five years later, the case remains unsolved and a new series of horrific murders occur throughout the city. As the murders escalate, Harley’s obsession with finding the depraved psychopath responsible leads her down a dangerous path. When the past and the present finally collide, Harley has to decide how far she is willing to go-and how many lines she is willing to cross-to solve these cases once and for all. In Gotham City, where heinous acts of violence are a daily occurrence, the GCPD relies on Harley Quinn, a young forensic psychiatrist and profiler, to consult on their toughest cases. But Harley is haunted by one unsolved case-the night she discovered her roommate’s body marked with the signature of a notorious serial killer known as The Joker. Five years later, the case remains unsolved and a new series of horrific murders occur throughout the city. As the murders escalate, Harley’s obsession with finding the depraved psychopath responsible leads her down a dangerous path. When the past and the present finally collide, Harley has to decide how far she is willing to go-and how many lines she is willing to cross-to solve these cases once and for all.