A young, idealistic college student at Columbia University who aspires to a career in children's television production. She often underplays her own ambitions to accommodate others but is deeply observant of the emotional currents around her. Her life is profoundly altered by the events of September 11, setting the stage for her subsequent romantic and personal decisions.

A charming photography student at Columbia University. Shaped by a volatile childhood and his parents' difficult marriage, he harbors intense fears of becoming like his father. He is driven to pursue a meaningful path, aiming to document the world's darkness and beauty as a working photojournalist.

A successful banker who is slightly older and more settled than Lucy's college peers. He is calm and considerate, moving at a steady pace that brings a sense of security to those around him. He enjoys making grand romantic gestures and planning surprises for his partners.

Lucy's close friend and roommate in New York City. She acts as a grounded sounding board for Lucy's romantic worries and provides practical advice on career challenges.

Lucy's caring brother who works in a science lab. He approaches life's emotional complexities with analytical logic, famously comparing romantic relationships to different types of chemical reactions to explain their longevity.

Gabe's former girlfriend. Her presence lingers in Gabe's life due to his strong sense of personal duty, creating early friction in his new social connections.

Jayson's girlfriend. Her steady connection with him serves as an example of a healthy, enduring relationship that deepens over time.

A friend of Lucy's who shares a summer rental house. She encourages Lucy to open up to new social possibilities and introduces her to new people.

A friend of Alexis who shares the summer rental house. Her social connections bring new people into Lucy's orbit during an important transitional summer.

A friend of Darren's who views Darren's romantic pursuits with a critical eye, often applying specific labels to the women Darren dates.

Kate's boyfriend. He shares in her social life and participates in group activities, providing a stable presence in Kate's world.