20. A Dark Knight: That Old Corpse

Complete story — includes the ending

Under seemingly posthumous orders from Jerome, his followers launch an attack on GCPD Headquarters. Nygma infiltrates the precinct and breaks Lee out, while Cobblepot and Grundy torture one of Jerome's followers to uncover the true mastermind and regain power. At his bunker, Jeremiah works on his self-sustaining energy generator and tells Bruce he is struggling against the toxin's insanity, leading to a confrontation at Jerome's grave. Believing the GCPD attack is a diversion from Bruce and Jeremiah, Gordon heads to the bunker and learns the day's events were a subterfuge orchestrated by Jeremiah, who has modified the generator into a bomb; Gordon barely escapes as the generator explodes. Revealing his true insane personality and his plan to tear Gotham down, Jeremiah leaves Bruce unconscious and steals more generators from Wayne Enterprises.