Nina
Nina is the first character we meet and the first person we see discover her box on the doorstep of her New York City apartment which she shares with her girlfriend, Maura. Nina is a journalist and very cautious, so her first instinct is not to open her box, and Maura follows suit. Once Nina and Maura open their boxes, they learn that Nina has a long string and Maura has a short string. Nina stays with Maura despite this knowledge without a second thought; however, we see how much Nina struggles to come to terms with Maura's string. Being with Maura brings out a courageous initiatory nature in Nina; this has been true since they first met, when Nina approached Maura in a karaoke bar.
Maura
Maura is a spontaneous and determined woman who has been Nina's girlfriend for two years. Maura's initial instinct is to open the box, but Nina convinces her to wait until more information comes out about the boxes. Eventually, Maura becomes firm in her resolve to open her box, prompting her and Nina to open their boxes together. Maura immediately wishes she hadn't, as she is surprised by her short string. Maura works at a publishing house and has gone through many jobs without finding one that is a good fit until her position at the Johnson Foundation near the end of her life. Following Nina's encouragement, Maura joins the short-stringer group at Amie's school. Maura is a passionate defender and active advocate of the rights of short-stringers. Maura dies of a heart abnormality after 10 years of marriage to Nina.
Ben
Ben is an architect living in New York City. Ben is on a plane when his string arrives. When he comes home to his girlfriend Claire he decides that he's not going to open his box. Claire opens both their boxes against his wishes and breaks up with him because of his short string—Ben has 14 years left to live. Ben's parents are teachers, and he eventually marries Amie, a teacher in whose classroom the short-stringer support group takes place, after several letter correspondences and a chance meeting in Nina and Maura's apartment.
Hank
Hank is a short-stringed surgeon at New York Memorial Hospital. Hank is devastated by the appearance of the strings because he feels that his role as a surgeon is obsolete as the birth and death of his patients are predetermined. Hank joins the short-stringer support group rather than the support group for people with very short strings because the latter group feels too sad of an environment for him. He keeps the truth from everyone except Ben and Anika, his ex-girlfriend who is a surgeon at the same hospital. Hank dies by jumping in front of an assailant's gun at Anthony Rollins's rally in NYC. Hank's lungs are donated to a patient at the hospital who has been waiting on a lung transplant.
Amie
Amie is Nina’s literature-loving little sister. Amie is an elementary school teacher at the Connelly Academy in room 204, the classroom where the short-stringer support group takes place after school hours. Amie decides not to open her box because she recognizes it as the type of regrettable mistake characters make in haste early on in a novel. Instead, she becomes the observer and secretly relishes the adventure ensuing in the world around her. Amie begins corresponding with Ben through letters without either knowing who the other is. Once Amie and Ben meet by chance in Nina and Maura's apartment, they begin dating. When Amie learns Ben is the short-stringer that she's been corresponding with, she almost cuts things off with him. But in the end, she chooses Ben, and they have two children together, Willie and Midge.
Anthony Rollins
Anthony Rollins is the leading presidential candidate due to his appeal to older long-stringers who are afraid of short-stringers. Anthony is married to Katherine, Jack's aunt, and is thus part of the Hunter clan. Anthony is guilty of being involved in the death of a boy through hazing at the frat house of which he was president in college. Anthony is invited onto the STAR Initiative by the former president and wins the presidency due to his image of being America's long-string guardian. Rollins has a long string.
Jack
We meet Jack, the youngest member of the Hunter clan, while he is finishing military school. He doesn't want to be in the military, but he doesn't have a choice as he comes from a long line of Hunter men who have served since the Civil War. His mother left him when he was young because she lost a custody battle with his father. Jack has been an outsider in his family all his life. He lives with his best friend Javier and has a long string.
Javier
Javier is Jack’s roommate, best friend, and one of the few Hispanic cadets on campus. Javier wants to make his patriotic parents proud; his parents are proud to be in America and grateful for everything America has done for them. Javier is extremely competent and a very dedicated cadet. Javier has a short string.
Sean
Sean is the facilitator of the short-stringer support group at the Connelly Academy. He is disabled and has a relatively long string.
Katherine Rollins
Katherine Rollins is Jack's aunt and Anthony's wife. She is part of the Hunter clan and helped care for and nurture Jack after his mother left. Katherine is dedicated to helping Anthony become President of the United States and has been working to get Anthony elected, along with the support of her family, since they met in college.
Wes Johnson
Wes Johnson is initially the leading presidential candidate before the debate in which Anthony calls for string transparency. Wes is the only candidate of color and he has a short string. Johnson starts the Johnson Foundation to safeguard the rights of short-stringers.
Captain Reynolds
Captain Reynolds joins Javier on a rescue mission to save two civilians whose plane gets shot down in enemy territory. Reynolds mails Javier’s confession letter to his parents after his passing.
Lea
Lea is a member of the short-stringer support group. She is pregnant and the surrogate of her brother and brother-in-law’s baby.
Anika Singh
Anika Singh is a high-performing surgeon at New York Memorial Hospital. She was in a relationship with Hank but ended it because she couldn’t give it as much attention as her career. Anika is supportive of Hank when she discovers his string and is one of two people who knows how short his string is.
Claire
Claire is Ben's ex-girlfriend who opens his box and tells him his string length.
Willy & Midge
Willy and Midge are Amie and Ben’s children.
Nihal
Nihal is a first-generation Indian-American short-stringer who is a part of the short-stringer support group.
