Carrie Hartnell was a special-ops soldier, working for a top secret program called Cobalt, who thought her husband Ross abandoned her. During a mission in Georgia she encountered something that deeply disturbed her. She volunteered for a program that would make her fearless. It also turns her emotions up to the extreme when it came to falling in love. Other effects included memory loss and increased strength. She fell off the radar for a long time. Years later, she found out that her husband Ross was still alive tracked him to Star City and killed him. Green Arrow thought that the unknown man was abusing his wife so he shot the arrow. Cupid picked up that arrow which began her obsession with Green Arrow.
Cupid first showed up on the scene in Star City at the scene of one of Green Arrow's fights. She picked up a broken tip of one of his arrows and carved the infamous heart with an arrow through it on her chest. She began killing off some of his notable enemies so that she may begin to fulfill his hearts desire. She is mentally unstable. Upon getting a new haircut, she cut out the eyes of the hairdresser, for the hair was cut so perfectly that she did not want anyone else to ever have the same perfect hair.
Small time enemies killed by Cupid include Big Game, Death Dealer, Vengeance, and Slingshot. This brought her to the attention of Star City's crime boss, Brick. When leaned of these killings, he set his men to find out who was behind them. Within minutes of sending a street junkie out to find Cupid, she shot the junkie in the head and proceeded to fire upon Brick himself. As this did not work, she had a back up plan in the form of a wrecking ball suspended from a crane. The crane cut through the building Brick was in and left him dead, cut in half at the waist. She had captured Merlyn from the police department, drugged him and lured Green Arrow to Star City Museum. Cupid had it arranged that Green Arrow, with a new-found darkness within him, would kill Merlyn and help himself achieve his hearts desire. Green Arrow did not follow through with Merlyn's death after seeing a way out of it and instead incapacitated him. This angered Cupid. She triggered an explosion. We next see her waking Green Arrow up underground.
She had chained him to the subway tracks and planned on dying with him in her arms so that it may be a romantically famous death. Black Canary, not liking her man taken away came to the rescue. Before admitting defeat Cupid slit an unconscious Merlyn's throat. Knowing that Green Arrow and Black Canary would not let him die (despite him being one of their worst and most destructive enemies) she used that chance to escape. She has started to aid the city during a riot, using a bow, that she admits she needs practice with. This is mainly to impress Green Arrow, but has not succeeded.
After spending some time in prison, she is broken out by her rival Black Canary because her life was believed to be in danger. Later she encounters Everyman who believes himself to be Green Arrow and they begin to work together against the real Green Arrow and company, with Everyman using the name "Dark Arrow". She is seen to still be obsessed with Oliver and only considers Everyman to be "good in a pinch". She eventually kills Dark Arrow, declaring their relationship "A rebound thing."
During a confrontation with Green Arrow and Black Canary, Cupid's comrades from Cobalt came for her, explaining her mental problems to the heroes and taking her away for treatment.