Atlanta falls victim to the fourth annual HORRORFEST. The weekend-long event is splattered with infamously grotesque B movies, appropriately named musical acts, costumes, parties, booze and everything else that makes the Halloween season so festive. Drag out your most disheveled outfit and adorn yourself with fake blood for the downtown Zombie Walk Sun., OCT. 4, where crowds of the living dead slump through the streets and spread terror on MARTA. Horrorfest concludes with the grand opening of the Masquerade's Chambers of Horror Haunted House, boasting a booze-addled full bar in the Splatter Lounge. Horrorfest: Oct. 2-4. Free-$8. See website for times. Lenny's Bar, 486 Decatur St.; and Plaza Theatre, 1049 Ponce de Leon Ave. www.atlhorrorfest.com. Chambers of Horror: Through Oct. 31. $15. Sun.-Thurs., 7 p.m.-midnight; Fri.-Sat., 7 p.m.-1 a.m. 695 North Ave. www.chambersofhorroratl.com.