A series of mysterious student deaths at Gotham University draws Harley Quinn out of hiding. When her investigation converges with the Batman's, the two former adversaries strike an alliance to take down the immediate threat- the Scarecrow!

As the Batman resumes his search for Rupert Thorne, his investigation intersects with that of Carrie Kelley, an amateur detective calling herself "The Crime Smasher"! Together, they team up to take down Gotham's underworld fixer, Mr. Zero!