"One by one."
Henry and Trish are getting married on Harper's Island, where they met and grew up together. Six years ago Henry's best friend Abby's mom was killed by a guy named John Wakefield on that island, and she damn near didn't come to the wedding because of it. But arrive she did, and it turns out that was a bad idea because now the wedding party are getting all kinds of killed and all the deaths seem to be Abby-related.
The first few episodes are kind of dull and very soap opera-y. It starts to pick up around episode six or seven, and then around episode eleven or twelve it took another turn and I kind of stopped caring again.
Harper's Island was interesting and entertaining, but it absolutely wasn't what I wanted it to be. There was too much interpersonal drama and soap operainess, not nearly enough murder mystery.
I have to give the show credit, though, in making me care about characters I didn't think I could ever care about. Most of them are snooty rich people but the writers put in the effort to make them human, and I actually cried at a few of the deaths.
The show also gave me really screwed up dreams, which is a total downside. Maybe I shouldn't have watched the whole series in one day.
End of line.