Maybe they should call him the Quartet Killer?

On this week's new episode of Dexter - which follows one of the best hours in the show's history - Dexter discovers something new about Arthur Mitchell.

We gave most of it away above, but the following trailer doesn't reveal any major spoilers. It just gets us excited for 9 p.m. this Sunday night...

[video url="http://www.tvfanatic.com/videos/lost-boys-promo/" title="Lost Boys Promo"] [/video]

Is this sneak peek not enough? Follow this article's jump for two clips from "Lost Boys."

[video url="http://www.tvfanatic.com/videos/lost-boys-clip/" title="Lost Boys Clip"] [/video]

[video url="http://www.tvfanatic.com/videos/at-the-doctor/" title="At the Doctor"] [/video]

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.