Sasha came to the United States, and specifically Gotham City, with her father Niko. Niko was a petty criminal who came to Gotham City because his brother Lev had made promises of opportunity. Sasha chose to come along because she always sided with her father against her mother. Her mother believed Niko to be a "no-good shiftless waster." Sasha would later come to believe her mother was perhaps right about Niko all along. But he was still her father.
After her father and Uncle Lev had a job foiled by the new Batman and Robin, they both returned home to Sasha ready to pack up and leave town. It was Batman they were afraid of, but their fears were misplaced. For their failure, Professor Pyg came, killed Uncle Lev and abducted Sasha and her father. They were taken to his hideout, a run down circus ground, where Pyg conducted his experiments on them. Sasha had to watch as Pyg turned her father into a "Dollotron" by grafting a freakish mask to his face and surgically altering him. The drugs and trauma reduced him to another one of Pyg's mindless and obedient servants. Then, the process began on her. It only progressed as far as grafting the mask to her face, mutilating her. Robin had found his way to Pyg's hiding place and gotten himself captured. Pyg stopped working on her so that he could focus on Robin, but Robin broke free of his restraints. During the distraction, Sasha attacked Pyg in a rage and lit him and the whole place on fire. Robin promised to save her, but he became too distracted with pursuing Pyg. She begged for him not to leave her behind, and he tried to reach back for her but tumbled outside with Pyg.
She managed to escape burning along with everything else. However, the entire ordeal had traumatized her. She looked like one of Pyg's Dollotrons now, as did her father. She found where he had been taken in the hospital, slipped into his room during the night, and smothered him to death with a pillow. This was when the Red Hood found her and promised her a way she could channel all that rage.
Scarlet was created by Grant Morrison and Frank Quitely in the very first issue of the Batman and Robin ongoing series. She was one of several new characters introduced during Morrison's run.
Major Story Arcs
Revenge of the Red Hood
This was how Sasha became Scarlet, the Red Hood's sidekick. She joined him on his viral marketing campaign of killing criminals and trying to supplant Batman and Robin's place in Gotham City.
She was afraid to try to remove the mask Pyg had put on her. If she attempted to do so, it could tear her face off or make it so no doctor could help her later. She asked Red Hood "Maybe it will dry up one day and drop off. You think?" He reassured her that whatever she decided to do about it would not make her any less special.
Working with the Red Hood led her into a confrontation with Robin, who had previous failed to keep his promise to save her. He was a much better fighter than her, but he was still only a kid. She surprised him with a taser shot and stabbed him in the side. She then rendered him unconscious with a blow to the head, helping Red Hood capture the dynamic duo.
The actions of Scarlet and the Red Hood had also garnered the attention of El Penitente who sent an insane assassin by the name of Flamingo to kill them. Flamingo had incapacitated Red Hood and Scarlet, and would have killed them if not for the intervention of Batman and Robin. During the fight, Robin saved Scarlet from Flamingo, taking five gun shots in the back. Scarlet was able to injure Flamingo, allowing Red Hood to defeat him. When Batman came to the injured Robin's side, Robin said "Just tell...tell the girl we're even."
Scarlet escaped the scene in the Red Hood's vehicle headquarters. As she is left Gotham City, the "Dollotron" mask appeared to peel away and fall from her face along with the "horror and madness" in her mind.
Streets Run Red
Months later, Sasha was abducted by an unknown party with an interest in Jason Todd. They held her captive as a means to control Jason and held her dressed in her Scarlet costume complete with mask.
Jason was sent to a corrections facility in Gotham rather than Blackgate or Arkham. However, it didn't take long for Jason to exact bloody justice on 82 inmates. The warden of the facility couldn't tolerate Jason's stay so he authorized Jason's transfer to Arkham Asylum. Unfortunately, Jason's transfer convoy was attacked by the Menagerie, a group of human/ animal hybrids. These creatures turned out to be Jason's rescuers and even though they killed the guards from the convoy, Jason was obliged to accompany them to freedom.
Jason asks Lionhead, the leader of the Menagerie, why they went through all the trouble to rescue him.
Lionhead informs Jason that someone else wants to meet him and if Jason does not comply then their employer will kill Scarlet. Once Jason heard his former sidekick's life was being threatened, he immediately springs into action. Jason and Lionhead tussle for a brief moment until the Dynamic Duo shows up. Dick knew that something might happen to Jason's convoy since Jason has made plenty enemies. The Dynamic Duo saves Jason from the Menagerie's grasp but not before Damian placed a tracking device on the Menagerie's getaway van. Jason informs the Dynamic Duo of Scarlet's current predicament and the Dynamic Duo agree to help Jason.
Jason and the Dynamic Duo go to the meeting seperately because the duo will serve as back up. Jason never meets the orchestrator of the Menagerie face to face but it is possible that this orchestrator is Satana the Tiger Girl. Then again, maybe she is related to Scarlet in some way because when Jason arrives, Scarlet is still alive and unscathed. The duo and Jason subdue the Menagerie and rescue Scarlet but the leader behind the Menagerie is never apprehended. Jason and Scarlet beat up the Dynamic Duo because they knew the heroes would most likely escort them back to prison after all was said and done. Jason and Scarlet escape in a helicopter while the Dynamic Duo remains tied up. Scarlet was given the option of being dropped off wherever she would like, but she wanted to stay with Red Hood as his partner.