Jason Todd was a young street orphan who first encountered the Dark Knight while attempting to steal the tires of the Batmobile. Bruce Wayne sees to it that Jason is placed in a school for troubled youths. But it turns out the school was secretly the main headquarters for a band of thieves. Jason earned the mantle of Robin a short while later by helping Batman apprehend the gang of thieves.

However, Todd does not wear the Robin costume (an improved version of) until after six months of training. Batman realized that while Jason doesn't possess Dick Grayson's acrobatic skills, he can become a productive crimefighter by channeling his rage. He also believes that if he doesn't help the boy, Jason will eventually become part of the "criminal element." Jason also aided Batman while Gotham City was temporarily overrun by Deacon Blackfire.

In Jason's first adventure as Robin, he encountered Two-Face, a villain that Batman has not told him much about. Curious, Jason studied up on Two-Face and discovers that he was responsible for the murder of his father, Willis Todd. The revelation fuels Jason's anger. When confronting Two-Face again, Jason attempts to strangle him. Once Batman discovers the source of Jason's anger, they are able to work it out and stop Two-Face together. However, this instance marks the first time when Jason feels unable to talk to Bruce about his problems; a trend that would continue until his demise.

As Jason's rage and dangerous behavior continue to grow worse, Batman has no choice but to suspend Jason from active duty. Angered by this decision, Jason walks out on Bruce and heads back to his old neighborhood. His old neighbor gives him a box of his mother's belongings and he soon discovers that Catherine Ann Todd was not his biological mother. Determined to find his birth mother, Jason uses his father's old address book and the Batcomputer to find three women who might be his mother. After following a number of leads, Jason finally tracks down his mother, Sheila Haywood, to Ethiopia, where she works as an aid worker. While Jason is overjoyed to be reunited with his birth mother, he soon discovers that she is being blackmailed by the Joker, who is using her to provide him with medical supplies. Sheila herself has been embezzling from the aid agency and as part of the cover-up she hands her own son, who arrives as Robin, over to the Joker. The Joker beats the boy brutally with a crowbar, and then leaves him and Sheila in the warehouse with a time bomb. Sheila and Jason try desperately to get out of the warehouse but are still inside as the bomb goes off. Batman arrives too late to save them and is only able to hold Jason's lifeless body in his arms. The bodies were taken back to Gotham City for burial.

For years, Jason's death haunts Batman. Immediately following Jason's death, Batman strips the Batcave and Wayne Manor of anything related to Jason, trying to forget the boy even existed. Once Tim Drake arrives and helps soothe Bruce's anger, Jason's old costume is put on display in the Batcave. When training to become the new Robin, Jason's rage and impulsiveness is used to remind Tim the importance of patience and doing the job correctly. Batman considers this his greatest failure: not properly training Jason in his role as Robin and failing to protect him from the Joker.

It is later revealed that Jason indeed had died at the hands of the Joker, but when Superboy-Prime alters reality from the paradise dimension in which he is trapped (six months after his death), Jason is restored to life and breaks out of his coffin, but collapses thereafter and is hospitalized. After spending a year in a coma and subsequently as an amnesiac vagrant, he is recognized by Talia al Ghul. She spends several years trying to help restore Jason to full health, but the mental damage appears too extensive. Jason's is still able to fight, due to muscle reflex, but he appears to have no awareness of the situation. Talia's father, Ra's al Ghul sees Jason as a lost cause and orders him to be eliminated. In a last ditch effort to save him, Talia restores Jason's health and memory by immersing him in a Lazarus Pit in which her father is also bathing. It is suggested at that exposure to the Pit's energies together with Ra's might have affected Jason's personality. On Talia's advice, Jason determines his death was never avenged, and prepares to confront Batman by traveling across the globe in the same path of training as his mentor.

Using the money from Talia and infuriated by her statement that he "remains un-avenged," Jason paid a group of mercenaries to help him return to Gotham. Once Jason arrives (during the aftermath of the event of No Man's Land), he enacts a plan to get revenge on Batman. He created a false arms trafficking of advance military arsenal, knowing that Batman would respond. This provided Jason an opportunity to plant a bomb beneath the Batmobile while Batman is on a stakeout for the arms deal. Batman enters the car and is at the boy's mercy, detonator in hand. However, Todd realizes that his former mentor would never know about his return nor that he would be Bruce's killer. Jason then decides to confront and kill Batman directly by traveling across the globe in search of a similar, yet more deadly type of training as Bruce received to prepare for that day. Todd learned the murderous arts from various masters around the globe. Such training includes firearms, poisons and anti-toxins, martial arts, and bomb-making.