A New York City mathematician at the beginning of his career meets a fourteen-year-old girl named Marcy. The two form what is essentially a romantic, quasi-sexual relationship. After Marcy and her mother take a two-year trip through Europe, she asks him to pick up her luggage from the Port Authority, but when he obliges, two men with whom she was involved abroad threaten him with knives for her address. She refuses to apologize when he brings her luggage to her, and, despite her being just sixteen, the two have sex. Afterward, they decide not to pursue a relationship of any kind, but from that point on, the mathematician finds himself looking out for her. Years later, after she returns from another trip through Europe, she puts down roots on the Lower East Side, renting an apartment and picking up Peter, a Greek immigrant who deserted the Navy and becomes her beau. Marcy becomes a solo dancer in Village coffeehouses until the very last days before she gives birth to his child. Their relationship is rocky -- Marcy has sex with other men, and when she tells Peter about one of them during the act, he snaps. Hours later, Marcy wakes the mathematician in the middle of the night to tell him that Peter has stabbed her one-night stand, Quincy. Luckily, Quincy hates the government and feels apologetic enough to not press charges, but when Peter, Marcy, and the mathematician visit him in the hospital, they fight bitterly over who works better with Marcy, who then runs away. Soon after, Marcy gives birth to Didi, her baby son, and becomes caught up in the countercultural movement. All the mathematician can do is try desperately to keep her life running. One night, the mathematician and his wife receive a call from Marcy: she started a fire in her tenement, and although Peter was able to save Didi, Marcy, and almost everyone in the building, he is badly burned. The mathematician and his wife care for Marcy and her son and visit Peter periodically. Eventually, Marcy, upon seeing the mutilated Peter for the first time, runs away to California and starts a cult called The Aesculapians. Peter, miserable and permanently disfigured, commits suicide in a hospital bathroom.