Clay, a high school junior, arrives home after school to find a package addressed to him resting against the front door. He opens it to find a set of seven tapes, each side numbered one to thirteen with the final side left blank. He begins to listen to the first side.
On the tape, Hannah Baker introduces herself. Clay is shocked: Hannah ended her own life weeks ago. She tells her listeners that she’s chosen the 13 of them because they each contributed to her decision to kill herself. After each person listens to the tapes, they should send them on to the next person on the list; otherwise, someone will publicly distribute a second set of the tapes. Clay thinks he must’ve received the tapes by mistake, but she describes the map that each of her listeners should’ve received, which matches a map he received in his locker a few weeks ago. Hannah encourages her listeners to visit the starred places on the map if they want to understand her better.
On the first tape, Hannah names the first person on her list: Justin Foley. Justin was Hannah’s first kiss in her freshman year, but soon after their kiss, Justin started spreading rumors that made people at school think Hannah encouraged Justin to do more than kissing. The rumors ruined a precious memory for her, helping Hannah’s reputation to spiral out of her control.
After listening to the first tape, Clay goes to his friend Tony’s house to borrow his Walkman. He starts to follow Hannah’s map while listening to the tapes. He arrives at the first star on the map: it’s the first house Hannah lived in when she moved to this town, but it’s also the house Clay visited a month ago when he witnessed a car crash involving an elderly man and had to run to the man’s home to tell his wife he was okay.
On the second side of the tape, Hannah names Alex Standall. Alex was the author of a list called “Who’s Hot/Who’s Not” in freshman year, naming Hannah under “Best Ass.” The day the list spread around school, Hannah went to Blue Spot Liquor to buy her usual candy bar and as she was paying, a boy walked in and grabbed her butt. On the next tape, Hannah names Jessica Davis. After the “Who’s Hot/Who’s Not” list was published, naming Jessica Davis under “Worst Ass,” Jessica confronted Hannah: she’d heard rumors about Hannah and Alex getting romantically involved. When Hannah tries to tell Jessica that Alex only pitted them against each other on the list to get back at Jessica because he and Jessica had had a relationship and broken up, Jessica slaps Hannah on the face, leaving a scar.
Next, Hannah names Tyler Down. A couple of years ago, she and Courtney Crimsen discovered he was taking photos of Hannah through her slightly open bedroom blinds. When they caught him—thanks to Courtney’s plan of luring him in by saying sexually suggestive things before suddenly opening the blinds—he zipped up his pants and ran away. After that, instead of leaving her bedroom blinds ajar so she could fall asleep watching the stars, Hannah kept them tightly closed.
On the next tape, Hannah names Courtney Crimsen. Courtney seems perfect from the outside, but Hannah thinks she’s only pretending to be nice. The day after Courtney and Hannah caught Tyler, Hannah expected Courtney to treat her more like a friend, but Courtney mostly ignored her. Then, the day of a big party, Courtney asked Hannah if they could go together. Hannah agreed, but quickly realized that Courtney just wanted a ride to the party. At the party, she found out Courtney was spreading the rumor that Hannah had something sexual hidden in her bedroom drawers. She left the party without Courtney.
Clay arrives at Tyler’s house. There, he finds Marcus Cooley, who offers him a rock to throw at Tyler’s window. Clay realizes Marcus must appear later in the tapes—he must feel like Tyler deserves the blame for Hannah’s death. Clay calls Marcus a “dick” and walks away.
On the next tape, Hannah describes the Oh My Dollar Valentines, an annual event at school that involves people filling in surveys about their romantic preferences and then paying to find out their best matches. The day the matches came out, Hannah got a phone call from Marcus, who told her she was on his list of matches and invited her to a date at Rosie’s. Hannah waited at Rosie’s for more than half an hour before Marcus arrived. He took her to a booth at the back of the diner and started touching her under her skirt without her consent. Hannah started to feel like she’d never get control of her life. Clay heads to Rosie’s but stops at the movie theater where he and Hannah worked together last summer. He realizes that he could’ve really connected with Hannah here, but he didn’t try hard enough.
On the next tape, Hannah explains that after Marcus left her at Rosie’s, Zach Dempsey sat down opposite her. She stayed silent for several minutes before he went back to sit with his friends, who laughed at him for failing to connect with her. Later, Hannah found out Zach was stealing the compliments from her paper bag in Peer Communications (a class at school in which everyone is encouraged to share notes of encouragement). On the tape, she tells Zach that he took away the only form of hope she felt she could rely on. After that, she dropped a question about suicide in the teacher’s paper bag, and when the class discussed it, they seemed annoyed that the person who suggested the topic didn’t come forward. Looking back, Hannah wonders if she suggested the topic as a way of reaching out for support.
Clay begins the next tape as he sees Tony walking out of Rosie’s and getting in his car but not driving away. On this tape, Hannah reveals that the poem everyone at school was sharing around and analyzing in English class was actually hers—Ryan Shaver, the editor of the Lost-N-Found Gazette, stole it from her and made copies. Clay leaves Rosie’s. Tony calls him over and tells him to get into his car, revealing that he has the second set of tapes.
On the next tape, Hannah tells Clay he’s not on the list because he did anything bad to her, but because she wanted to go out with him. She says that the next few tapes will focus on a big party a few months ago. That party was the only time she and Clay really connected, but even though they got along well and started to kiss each other, she couldn’t bring herself to fully open up to him and instead pushed him away. The next tape continues the story of the party: after Clay left the empty bedroom where he and Hannah were kissing, Justin brought Jessica in and tucked her into bed. Jessica was too drunk to even talk properly. After Justin left the room, he let Bryce Walker in, and Bryce raped Jessica, who was unconscious by then, while Hannah hid in a closet.
On the next tape, Hannah says that Jenny Kurtz, a cheerleader from school, offered to drive her home from the party. During the car ride, Jenny crashed into and knocked over a stop sign. Hannah tried to get her to call the police, but Jenny refused and left Hannah on the side of the road. Hannah tells Jenny that, by brushing off the accident, she got away with more than knocking down a stop sign, because while the stop sign was missing, two cars collided at that intersection, resulting in the death of a high school senior (this is the same collision Clay witnessed).
On the penultimate tape, Hannah admits that she’s a vital part of her own decision to end her life. She tells the listeners about another party after the big one she just described. She didn’t attend this party, but she walked past the house afterward and saw Courtney and Bryce in the hot tub. They invited her to join them, and she did, though she knew she shouldn’t. In the hot tub, Bryce started to touch her and eventually have sex with her. She didn’t resist him, but she didn’t consent, either. Clay arrives at Eisenhower Park which contains the rocket slide where Hannah had her first kiss. He climbs up the rocket and plays the final tape.
On this tape, Hannah records her meeting with Mr. Porter, a guidance counselor at school. She tries to tell him how hopeless she feels and to explain the sexual assault she experienced in the hot tub, but he tells her she might need to just move on. Hannah thanks Mr. Porter and leaves; he calls after her, but ultimately leaves her be. Clay plays the unlabeled B side of the tape, on which Hannah only says, “Thank you.” Clay leaves the park and goes to the post office to mail the tapes. By now, it's morning. When he arrives at school, he sees Skye (his middle-school crush, who he’s noticed becoming more distant and antisocial) walking down the hall. As she fades from view, he decides to go after her, calling her name.