Robin was working out in the cave. Batman, not approving of his choice in music, turned off his boombox. Wanting to appease his young ward, Batman offered to take him out and help discover the true nature of his favorite singer, Izaak Crowe, who'd been accused of blowing up a studio. They visited his promoter and learned that he'd had another recent freak out and believed he was in the company of a long dead rock legend.
They caught up with the singer at a mall music store. He had gathered followers and was demanding the store carry his album and give it to kids for free. Security got involved and shots were fired. Batman and Robin were too late - Crowe and his gang escaped, though Crowe himself had a bullet wound in his shoulder. Crowe and his girlfriend / bass player stopped at a drive-in theater to watch some Elvis movies. She snuck off and called their status in - she was in on the situation.
Batman brushed up on rock and roll history and realized Crowe and his followers were headed for the home-turned-theme-park of their "god." They got there as the angry mob began fighting the police. Shots were again fired as the body of their fallen idol was removed from its resting place. Crowe again escaped.
Batman, trying to show Robin that rock music caused insanity, took him to Arkham. Robin rebelled and ran away. He caught up with Evangeline - Izaak's bass player and lover. He tried to convince her to help him save the man, and realized she was partly behind the madness. They got to the roadblock where police and followers were holding out for Izaak to arrive. Batman got there at the same time. Crowe was killed in a shoot-out by the police. Batman almost snapped.
They went after his promoter / manager, who was flanked by dozens of impersonators. Roy Lazarus committed suicide running from the dynamic duo.