Clay Jensen doesn’t know why Hannah Baker committed suicide, but he’s about to find out. Before she died, Hannah recorded a set of cassette tapes, one side for each of the 13 reasons she chose to take her life. Each reason relates to a person. Each of those 13 people must listen to her tapes, then pass the set on to the next person. And Clay is one of them.
When the tapes arrive in the mail, Clay is confused. Aside from making out with Hannah at a recent party, he didn’t know her well. Despite her loose reputation, he really liked her, and he would never have done anything to hurt her. Surely there was a mistake; he can’t be responsible for Hannah’s suicide. But Hannah has threatened that the tapes will be made public if he doesn’t follow her instructions. So he pops the first tape into an old stereo system in his parents’ garage.