Joker marks his return to Gotham City by attacking the GCPD and recovering his preserved face, killing 19 police officers in the process. He later televises a warning, via the son of his first recorded victim, that Mayor Hady will die that night, referencing another of his earliest crimes. However, the police assigned to protect Hady are killed by a combination of chemicals while Hady survives. Batman analyzes the chemical compound and finds three inert ingredients whose initials spell A.C.E., leading him to the ACE Chemical plant where Joker was originally disfigured. He encounters a person dressed as the Red Hood, one of Joker's aliases, and is struck by an oversized mallet that pushes him into an empty chemical vat; the Hood, revealed to be Harley Quinn, warns Batman that Joker is not the same.[5] Batman manages to escape the vat before it can fill with chemicals.[6] Elsewhere, the Joker attacks Alfred Pennyworth.[5] Each issue of Batman also contained a short backup story; in Batman #13, this story sees Joker preparing Harley to meet Batman in the chemical plant.[7]
