Young Jimmy Santini accompanied his father on a trip to investigate possible illegal waste-dumping in Carlsbad Caverns National Park, where his father was killed by polluters, either shot in the back or by falling to his death in a deep cavern (the details in Jimmy's diary were very murky). Jimmy was left alone, lost in the caverns for an unknown amount of time, where to survive he drank chemically polluted water. Eventually, he was rescued, and returned to his mother. However, the chemicals began to take effect, and Jimmy sprouted wings, and his mother proclaimed him a demon. Jimmy ran away, further mutating as he wandered the country, stealing food in order to survive. Eventually, he came to New York and made his home under an old pier. Jimmy began stealing food from people dining on rooftops, scaring people away with his appearance and cries, to avoid hurting anyone. His appearance caused the press to dub him "Batwing."
Jimmy swooped down upon New York City Councilman Randolph Cherryh and his girlfriend as they dined on the rooftop of Cherryh's high-rise. Terrified, Cherryh told Batwing "Take the girl! Not me!" But Jimmy just stole a few apples from the table. Humiliated, Cherryh decided to put a high bounty on Batwing. Peter Parker, who was having financial problems at the time, decided to go after the little bat creature. He arranged for a large party at Randolph's home, hoping to lure Batwing into the open. It worked, but Spider-Man was horrified when Cherryh's men began shooting at the creature. He webbed their guns up, and then took off after the fleeing creature. Batwing scratched him several times with his claws while trying to escape, and when Spider-Man hit him back, he fled back to his home under the pier.
Spider-Man followed him, and discovered that Batwing was only a frightened child, stealing food to survive. He read in Jimmy's diary about his history and offered to help him, but the boy was scared and burst through the pier, right into the hands of Cherryh and his men, who had secretly been following in a helicopter. The Councilman didn't care that Jimmy was just a kid, and was about to kill him when Spider-Man intervened, webbing down his men. Batwing flew off, terrified, despite Spider-Man's offer to get Reed Richards or Henry Pym to help cure him. Cherryh threatened to ruin Spider-Man's life for interfering, but Spider-Man just told him off, webbed his mouth shut, and stuck him in a garbage can. When the police arrived and searched Batwing's lair, Spider-Man hoped that when they found the diary, they might be able to get help for Jimmy.
Spider-Man struck a friendship with Batwing, bringing him food and companionship even though he still rejected help since he was still afraid of people like Cherryh.
Spider-Man later asked his friend Dr. Curt Connors to use his expertise to help cure Jimmy. However, an accident in the lab caused Connors' villainous alter-ego the Lizard to emerge, and he battled and defeated Spider-Man before fleeing into the sewers. Spider-Man managed to create an antidote and went into the sewers to cure Dr. Connors. After curing Dr. Connors, Connors and Batwing left New York on train to go somewhere where they can find a cure in peace.
While attempting to cure Jimmy, Dr. Connors failed and Jimmy reverted to Batwing. He returned to New York and engaged Spider-Man in another battle. Spider-Man was unwilling to hurt Jimmy. Jimmy, with his father dead and his mother rejecting him, just wanted to die. Spider-Man tracked down Jimmy's mother and told her that he was still her son, creature or not, and that she was wrong to reject him. Just as Batwing was about to be shot by the NYPD, Jimmy's mother intervened, telling her son that she loved him. Upon hearing this and knowing that he was loved, Jimmy reverted back into his human form and the police backed off. Jimmy went home with his mother, finally receiving the love that he had needed so badly.