Blood Simple, the 1984 black-comic thriller that introduced director Joel Coen and his brother and co-writer, Ethan, to the screen, has been restored, re-edited and rereleased, and that's something worth cheering about during these dog days. The Coens, then as now, are alive to the possibilities of movies. So savor their technique and the sizzling performances of Frances McDormand as an adulterous wife, Dan Hedaya as her vengeful husband and M. Emmet Walsh as a private detective from hell. One