This is it—the story you’ve been waiting for: the secret origin of comic’s newest, deadliest and most insanest villainess, Harley Sinn! Why is she so obsessed with Harley? How did she manage to become a super-villain? And what is her connection to the Gang of Harleys themselves? Find out this issue! Plus...Harley’s still kidnapped! So there’s that.

The Gang of Harleys are on Harley Sinn's Island of Horrible Death, looking for their kidnapped leader Harley Quinn and are currently in a losing battle against robotic versions of Poison Ivy, Catwoman and Power Girl. Then Harlem Harley gets an idea, "run for your lives!" and run the gang does right into the Eggy Landmine field. This idea works and the robots are destroyed.

The gang soon finds Harley Quinn being attacked by murderous mutant goats. Wanting to help Queenie gets an idea and grabs Harvey Quinn leaving the rest of the gang to defend their leader. When Queenie and Harvey return they have weapons from robots they recently destroy and use them against the goats.

After regrouping Harley Quinn decides to take the fight to Harley Sinn. Meanwhile Harley Sinn gets her army of Sinndicates ready to take down Harley Quinn.

Also interlaced in the story is the origin of Harley Sinn.