Batman Vol 1 #327

Batman, who is disguised as Shank Taylor, recovers from the sedative and finds himself locked in Arkham Asylum. He frees himself from his strait-jacket, picks the lock of his cell door, and prowls about the halls of the insane Asylum. He can find no clue as to who is responsible for the prisoner-escaping racket, but unable to find hard evidence, he returns to his cell. His activities have been monitored on closed-circuit television by Professor Milo, who has taken control of the asylum and now knows him to be the Batman in disguise. Milo later has "Shank Taylor" brought to him and explains that the real director is now in a padded cell.

Milo's current scheme is to release certain Arkham inmates, have them rob for him using their specialized talents, and readmit them to the asylum after the jobs are done. When he offers "Taylor" the chance to commit jewel robberies for him, Batman refuses, but had alreadt secretly-administered a strong drug. Back in his cell, Batman breaks free and goes to the Joker's cell, where he takes a Batman costume and gets ready to confront Milo, when the drug suddenly kicks in. Batman awakens moments later to find himself confined in a new strait-jacket from which he cannot escape. Milo and the other inmates surround him and try to convince him he is a madman who thinks he is really Batman.

The ploy almost works until Batman notices in a mirror that his pupils are dilated, and deduces that he is still drugged. Batman takes out two of Milo's guards even while bound, convinces "Joan of Arc", another inmate, to cut him free, and goes after Milo. The villain emerges from his office in a protective suit and helmet, and smashes a vial of insanity-producing gas. Batman backs off, but the other inmates have followed Batman as their leader and surround Milo, before beating him, breaking his helmet. When the gas dissipates, Batman finds that Milo is a victim of his own formula, now hopelessly insane.