How It All Goes Down
Everything starts with Blue, a teenage girl who lives in a big house full of psychic aunts (yes, really) and her mother. She's been told since she was a little kid that her true love will die if she kisses him, which is definitely one way to keep your kid from ever going on a date.
Blue goes to church with her Aunt Neeve on St. Mark's Eve, which is when the spirits of those who will die in the next twelve months come through. Even though Blue normally has no psychic ability (other than making everyone else's magic stronger with her presence), she sees the spirit of a boy named Gansey—and Aunt Neeve tells her that this is because he is either her true love, or she will kill him. Uh-oh… That's no good.
Blue eventually meets Gansey and his group of loyal friends: Adam, Ronan, and Noah. She doesn't take to them immediately because they go to Aglionby, the rich all-boys prep school, and she sees them as condescending snobs. But slowly she starts to develop a friendship with them, especially with Noah and Adam (who also doubles as her romantic interest), and she joins them on their quest to find the ley lines (a.k.a. spiritual energy lines) and the buried Welsh king, Glendower.
Gansey's been on a mission to find this Glendower dude since he was a little kid and almost died of hornet stings. He had a vision about how he was being allowed a second chance at life in order to keep looking for Glendower, and he's not going to give up on the quest.
In the meantime, the boys' weird Latin teacher, Barrington Whelk, is also looking for the ley lines. He wants to perform a ritual sacrifice so that he can gain all the power ever. Whelk looked for the ley lines when he was a teenager at Aglionby, and even tried to perform the ritual after his family lost all their money. In doing so, though, he killed his best friend Noah as the ritual sacrifice… and it didn't do anything.
Yes, Noah—as in the same Noah who hangs out with Gansey and his friends. It turns out that their dear buddy is actually a ghost, which comes to light once they discover some magical areas on the ley line and find Noah's body.
Once this happens, the raven boys and Blue go on a mad quest to reach the ley line and stop Whelk from completing the ritual, since if he does, he'll be super powerful and hard to defeat (just like a video game villain). Adam is having some family issues at the same time—he's the one scholarship kid from the Aglionby group and lives with an abusive father—and he wants to do the ritual for himself so that he can be on an even playing field with his friends.
Adam sneaks off to Cabeswater, the magical place they've discovered, but when he gets there, he finds Whelk getting ready to sacrifice Blue's Aunt Neeve. He pulls out his dad's gun to threaten Whelk, but Whelk forces him to throw it into a bush. Dun dun dun…
Gansey, Blue, and Ronan get to the scene just in time to see Adam throw himself into the pentagram and sacrifice himself. Whelk tries to shoot him, but it doesn't work, and then a bunch of magical creatures come out and trample him to death. Adam remains untouched, and as they are turning to leave, the trees (which speak in Latin, apparently) tell the boys that there is an old king buried along this ley line, and they believe that he belongs to Gansey. Well, hello Glendower.
Later on, they attend Noah's funeral. While there, Noah whispers in Blue's ear that she should deliver a message to his parents, and she finally relents… even though it makes her look kind of crazy. That afternoon, they dig up Noah's bones and rebury them on the ley line so that he can become a more solid ghost again. He appears, and the raven boys and Blue are all together again.