Candy is a beautiful young painter in the first throes of love with a sometimes-poet named Dan. Their life is so romantic and their love so intoxicating that they care only for pleasure. Heroin, they discover, intensifies their mutual passion and allows them to get lost in the moment, and "using" becomes a ritual that makes them feel special.
In time, their habit supersedes all other aspects of their life together. They beg, borrow, and steal to pay for their next fix, and when there is nothing left to hock, they take more desperate measures. Candy sells her body. Dan lets her, and, imperceptibly, they cross a boundary as they exit Paradise and enter Hell.
As the grip of their habit grows, they affirm their lover's vows by getting married. Their big day passes in a drug-induced haze of bliss. Candy's parents, conservative, middle-class folk, are bewildered by the newlyweds' strange behavior. They watch their daughter's decline, sensing that something is wrong, but incapable of stopping her.
Candy and Dan's drug addiction becomes inseparable from their emotional addiction to each other. Their love, like the heroin they crave, is dangerous and destructive. When Candy suffers a nervous breakdown and ends up in rehab, the lovers face a difficult choice--their relationship, with all of its terrible highs and lows, or a second chance at life?