It's okay to let yourself be a little happy, Jim. 
Detective Comics #879 is an issue of the series Detective Comics (Volume 1) with a cover date of September, 2011. It was published on July 13, 2011.
Synopsis for "Skeleton Key"
Commissioner Gordon visits Leslie Thompkins at her clinic, and she tells him about how helpful James Jr. has been. He's even volunteering to do the nutrition runs, bringing baby formula from the manufacturer to new parents. But Gordon remains suspicious of his son's new leaf and asks Babs to analyze the new drug that James Jr. has been taking. Barbara discovers the Diamaxyne has been altered to do the reverse of what it should, and while it is too weak to affect an adult, it could turn a child who ingested it into a psychopath.
Gordon realizes that is why James volunteered to make the nutrition runs. Gordon goes to his son's apartment to confront him, but James isn't there. Gordon finds a box full of keys from James's past victims, including the bat key chain owned by Barbara's friend Bess Keller who went missing fifteen years ago. Harvey Bullock tells him the Joker has escaped.
Appearing in "Skeleton Key"
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