From TV Guide, tonites episode of Heroes will be the finale until the show returns early in 2007.  Chapter 11 “Fallout” has the following plot description:

“The heroes struggle to come to terms with the Texas tragedy; more is learned about the nuclear bombing predicted in Isaac’s painting; Matt and Audrey (Clea DuVall) pursue a new lead in their hunt for Sylar; Niki makes a difficult decision, which will allow her to keep her family safe.”

as well as:

“The tragic events in Texas have sad, serious repercussions for many of the “heroes,” their families and friends. Meanwhile, shocking details about the moments leading up to Issac’s (Santiago Cabrera) predicted New York City nuclear bombing are revealed. Later, Issac’s newest painting has fascinating future implications for a hero in crisis. Suresh (Sendhil Ramamurthy) takes the first steps along his new path. Matt (Greg Grunberg) and F.B.I. Agent Audrey Hanson (guest star Clea DuVall) pursue a break in the Sylar case. Horrified by Jessica’s recent actions, Niki (Ali Larter) makes a tough decision to protect her family.”