Oliver Vartran is an 8 year-old kid on his way home from school in a world where dark fantasy and high technology exist together. Today is going to be a memorable for a lot of reasons: you're going to summon a demon, your mother is going to be murdered, and a 10-year plague, known as The Decade is about to begin.
The story then jumps to 18-year-old Oliver chatting with his gay best friend Kael, who has just found him a lead on the 10-year-old case. And it's projected that the plague will end within the week! And Oliver has just found out that he's from a long line of demon hunters ... oops. In any case, things are suddenly looking up even if you were adopted by your mother's murderer (no, this isn't a spoiler, Columbo. You have to prove it ;) ). And that's just episode 2 of a 5 episode game.
The setting and art are gorgeous. The characters are entertaining. Putting together the mysteries of the series (as there are many different pieces you need to put together) is satisfying. There are several minor side quests and at least two different endings depending on if you play as a paragon or evil incarnate.