Ruby is the story Ruby Simmons, whose kleptomania propels her towards a life of inevitable vice, addiction and criminal behavior in the fast laneĀ. Her tale begins with the overwhelming joy she experiences in stealing a small heart-shaped red pincushion at the tender age of six. Almost from the beginning, the pleasure she takes from stealing, and her precocity, allows her to manipulate others to get what she wants.

As she grows up, although she is very bright, she has little interest in school. She is one of the smallest girls on the playground and after being forced into a fight, she discovers her own tenacity and a proclivity for battle. As she goes into the fifth grade, accompanied by a lackey drawn into her orbit, they are caught stealing from a department store.

In the twelfth grade, she and her best friend Curtis, a sissy, are introduced to some boosters, and dazzled by glamour and quick money, they choose the streets over school and drop out just months before graduation. Guided by Velma, a veteran booster, Ruby's world opens up and she and Curtis move to Los Angeles with her. In LA, she meets her first love, Darryl. Following a tempestuous relationship, Ruby finds herself rejected, alone, and pregnant.

She returns home to San Francisco, where she gives birth to Darryl Jr. For a brief time she tries to be a good mother, but it's not long before she's lured back and becomes involved with Renard Manning, a smooth-talking handsome dope-runner. She drops everything and accompanies him to New York City. Plagued with guilt she avoids calling home, and her abandonment of her son haunts her all the time.

After Renard's businesses deal goes awry and he is imprisoned, Ruby is left at the mercy of Renard's friend Fast Eddie, a pimp, and his stable of prostitutes, Sandra, Carmen and Ruthie. And when her growing addiction to heroin sours her working relationships, she is unable to make money by boosting.

At one of her most vulnerable moments, she is seduced by Sandra and pulled into Eddie's stable. It isn't long before she falls into an abyss of heroin addiction and prostitution, which leads her to befriend a series of junkies. When Eddie's house is busted for prostitution, she is arrested, along with the other girls, and held in detention long after the others have been released, and thereby forced to kick. She finds herself clean for the first time in months, but it isn't long before she falls off the wagon, worse off then before.

In a search for stability, she hooks up with Duke, a renowned heroin dealer. Their relationship starts off strictly business, but they grow to love each other and eventually marry. When Ruby overdoses and subsequently finds herself clean again, she and Duke, who never uses his product, slip into a fantasy of normal life, insofar as that is possible, until the next time the doorbell rings.

During this time, Ruby is ecstatic to find out that she is pregnant. But her joy is short-lived. When Duke is busted, she steps into his shoes and starts using again to cope with the stresses of the business and her pregnancy. When her son is born addicted to heroin, he is taken away by social services.

Distraught and unable to shake her depression, Ruby returns to dealing with a vengeance. In her attempts to make enough money for Duke's defense (eventually futile) and assuage her guilt over the loss of her new son, she becomes increasingly reckless. Pushing the throttle to the floor, she eventually crashes into the inevitable wall.