So, this is based on a young adult novel by the same name (well, I think the novel spells out the thirteen, but same diff). It's about a teenage girl named Hannah who kills herself (not a spoiler, she's dead at the start of the series) and sends thirteen tapes around to the thirteen people who, she feels, pushed her to the point of suicide. Each episode is a different tape, and we see, in flashbacks, what happened to Hannah, and we see the fallout of her suicide in the present. The main character is a kid named Clay who had a crush on Hannah and can't for the life of him figure out why he is on the tapes since he never really wronged Hannah in a huge way.