structural:scholar_edition, quality:corruption, structural:expansion
Batman: Hush

In the 12-part storyline Batman: Hush, it is revealed that Riddler suffers from cancer (specifically a brain tumor), which also afflicted the mother of Dr. Thomas Elliot. Riddler uses one of Ra's al Ghul 's Lazarus Pits to cure himself and offers Elliot the chance to cure his mother as well, provided he pays a large sum of money. However, Elliott is, in fact, eager for his mother to die to inherit her fortune. Elliott, who goes on to secretly become the masked criminal Hush, explains he wants to get revenge on his childhood friend Bruce Wayne. The two of them agree to work together and Riddler sets Killer Croc, Poison Ivy, Harley Quinn, Joker, Clayface, and Scarecrow out to destroy Batman, with Ra's al Ghul, Talia al Ghul, and Lady Shiva being temporarily drawn into the scheme as well.

During the psychotic break that follows exposure to the Lazarus Pit, the Riddler deduces Batman's secret identity; he then reveals his knowledge to Hush. He has Clayface shapeshift into the form of Batman's (presumed dead) protégé Jason Todd to torment Batman, who is haunted by the former Robin's death. Batman first thinks that Riddler had stolen Todd's corpse and hidden it, but it was revealed in a later storyline, Batman: Under the Hood, that Todd was alive the whole time and had personally played a role in Riddler and Hush's scheme. When the Riddler threatens to expose Batman's secret identity, Batman mockingly labels it an empty threat. He points out that if Riddler revealed the answer to the riddle "Who is Batman?", it would become worthless, something Riddler would not be able to stand. In addition, Batman warns him that if he reveals the secret, it would give Ra's al Ghul a vital clue that he used a Lazarus Pit without his permission, and the League of Assassins would subsequently retaliate against him.