The Measure begins with a prologue, describing how every person over the age of 22 in the world receives a wooden box engraved with the phrase "The measure of your life lies within." The first chapter, "Spring," opens with Nina, a journalist in New York City, discovering her box. Nina lives with her girlfriend of two years, Maura, and they learn that Nina has a long string and Maura has a short string, giving her only 10 years left to live. Ben is a young architect whose girlfriend opens his box against his wishes and tells him he has 14 years left to live before breaking up with him. Hank is an ER doctor who is resigning from his hospital due to feelings of growing impotence. When Hank learns that he is at the end of his string, he decides to take his own advice and join a support group. Amie, Nina's younger sister and a teacher at Connelly Academy, finds a writing exercise in her classroom and realizes that the short-stringer support group is being held at Connelly Academy. She writes a response on the piece of paper—discussing a couple separated during WWII—and this begins an anonymous correspondence with a man who turns out to be Ben. Maura and Hank are also in the support group.
As people begin coming to terms with their strings, violence at the hands of short-stringers increases and is extensively covered by the media. A shooting happens during Hank's shift at New York Memorial Hospital at the hands of a short-stringer. This leads members of the public to begin to question whether short-stringers have become a threat.
In the second part of "Spring," the public learns that the strings are real and foretell the length of their life. Long-stringers begin partaking in risky behavior without realizing that there are consequences besides death. People see short-stringers as invincible and dangerous because they will not live to face the consequences of their actions. We meet Anthony Rollins, a Virginian congressman who has married into the Hunter clan of men who have served in the army since the Civil War. His wife is Katherine, a woman who has raised her nephew, a young man named Jack whose mother left. Jack is an unhappy army cadet who lives with his best friend Javier. Katherine and Anthony frequently ask Jack to join them on the campaign trail in his cadet uniform. Sometimes Jack obliges because he loves his aunt, but he hopes that the arrival of the strings will kill Anthony’s presidential campaign. Anthony learns that Senator Wes Johnson, the candidate currently polling in front of him, is a short-stringer. Anthony attempts to use this information in the first primary debate of the season by calling for string transparency for all candidates. He reveals his string to the audience and is booed, but this display on national television causes a stir in the United States. After this display, there is a bombing outside the Capitol by a short-stringer. Ben and Amie grow closer and share more vulnerable details in their letters, and Maura confesses to Nina she feels that her string is taking away her ability to choose how her life plays out.
In "Summer," Anthony is rewarded for his display on television by being asked by the president to join his task force. They instate the STAR Initiative which requires string transparency for all military personnel. Jack offers to switch strings with his short-stringer roommate Javier so Javier can fulfill his dream of going to combat and Jack can avoid it, and Javier eventually agrees. Following Anthony’s actions at the presidential debate, he holds a rally in New York City which the short-stringer support group attends to protest. At the rally, an auburn-haired woman attempts to shoot Rollins, but Hank jumps in front of the gun and is killed. He is portrayed in the media as having saved Anthony, rather than being someone who was there to protest him, and the public sees Anthony as a hero—the guardian of the long-stringers. Maura is anxious following Hank's death because he is the first person in their support group to die, and she's hearing stories of short-stringers plagued with anxiety when approaching the end of their string. The science is out, and the calculation for string length is more precise. The death date range shrinks from a few years to a month.
"Fall" opens with Amie returning for the new school year and seeing the differences the strings have caused at her school. Enrollment has decreased as students' families adjust their lives to their strings, and the school fires a teacher for going against school guidelines when she gives a presentation about short-stringers to her senior class. The disdain toward short-stringers is rising: the first gun law to make it through Congress in years is one limiting short-stringer access to guns. Maura feels stuck, so she and Nina go on a trip to Venice. In Venice, Nina proposes and Maura says yes. Senator Wes Johnson announces that he is a short-stringer, but Anthony Rollins overshadows his speech by pledging his support towards short-stringers, citing his nephew Jack as leverage. Because Jack isn’t willing to stand up to his family, the biggest argument Javier and Jack have had in four years of friendship ensues. Javier decides to leave early for pilot training instead of staying with Jack, but Jack gives Javier the Jewish prayer card his grandpa Cal gave him before Javier leaves. The Rollins campaign informs Anthony that he does have a connection with the assailant at his rally: Anthony was president of the fraternity that hazed the shooter's brother to death 20 years prior.
Ben and Amie meet at Maura’s apartment, and they begin dating. Ben eventually realizes that Amie is who he’s been writing letters to, and after meeting the woman to whom Hank donated his lungs, he finds the courage to tell Amie the truth. Freaked out by Ben's short string, Amie doesn’t know what to do, so she asks Nina to come over and talk. Nina can’t believe that Amie would stop speaking to Ben because of his short string, and Amie judges Nina's logic when she tells her she proposed to Maura. This heated argument leads to Amie being uninvited to their wedding. When Jack is in New York City, he prevents an attempted hate crime against a Johnson canvasser and realizes Javier's concerns are right. He decides then that he’s going to make good on his promise to Javier and make him proud.
"Winter" opens with Jack at a televised event for his uncle, the biggest event of the Rollins campaign. Minutes into Anthony's speech, Jack takes the microphone from him and tells everyone that his uncle doesn’t care about short-stringers and he only cares about winning. He goes on to say that we’re all humans despite our strings. His action affects Anthony’s numbers with young undecided voters and inspires a South African girl to make a speech about the strings that goes viral, sparking the #StrungTogether Movement. Nina and Maura decide to get married at City Hall and have a wedding dinner afterward at a nearby restaurant. Amie is re-invited because she recently went to Nina and apologized profusely. At Nina and Maura‘s wedding dinner, Amie sees Ben for the first time since receiving his letter. She thought she would ask him to be friends, but instead she asks him to dance. While dancing with him, she is afraid that she can’t handle his short string and runs into the street, only to hear "Que sera sera"—a song that she has identified in a letter to Ben as being a symbol of hope—playing in the streets of New York for the first time since the arrival of the strings. Jack and Javier make peace at a veterans' bar just in time for the New Year's countdown. At a #StrungTogether event happening at the same time throughout the world to recognize short-stringers that are still alive, Lea, another member of the support group, goes into labor. She gives birth to twins at the hospital with everyone from the support group there.
At the end of the main narrative, Amie and Ben are together and Ben proposes to her in Central Park, to which she says yes. The Strung Together movement commissions a sculpture to celebrate the first anniversary of the arrival of the strings, a tree sculpture depicting the tree of life with strings from 500 people. A year after the arrival of the strings, the newest generation of 22-year-olds is increasingly deciding not to open their boxes.
In the epilogue, titled "Several Years Later," we learn that Javier died acting as a decoy in a civilian rescue mission. He died reading the prayer on the Jewish prayer card Jack gave him, and we learned that this prayer card came from the military couple that Amie and Ben wrote their first letters about. Jack receives the confessional letter Javier wrote to his parents and decides to take it to the Johnson Foundation—a nonprofit started by the senator that Anthony beat in the presidential race that is dedicated to establishing legal protections for short-stringers—so that they can release the letter to the public. Jack's action leads to Anthony losing the re-election. Meanwhile Maura, the Director of Communications at the Johnson Foundation, helps to get the STAR Initiative defeated in the Supreme Court. Jack became a minor celebrity after the release of the letter, and now works at a nonprofit supporting veterans with PTSD. He’s married and expecting his second child. Maura dies of a rare heart abnormality and Nina gives the eulogy at her funeral. Nina focuses on Maura‘s life rather than her death in her eulogy and measures Maura's life based on impact rather than length. Amie and Ben have two children, Willie and Midge. At the end of Ben’s life, he feels satisfied that Claire told him about his string because he gets to live the rest of his life with the people he loves. While Ben has been preparing his family for his death, no one is prepared for Ben and Amie dying together on their way to Ben’s appointment. After Amie's death, Nina finds Amie's string, which is the same length as Ben's. Nina adopts Willie and Midge without hesitation and moves into their family home. Nina is grateful that Amie never opened her box so that she didn’t have to live with the anguish Maura lived with.
This book closes 15 years after the initial arrival of the boxes, and the public perception of short-stringers has changed from dangerous to purposeful and open to life. Fewer and fewer people are deciding to open their boxes, which Nina interprets to mean that more people are deciding to choose the measure of their life themselves. The Measure ends with the man on his bicycle playing "Que sera, sera" as a further symbol of hope.
