Editor's note: This article has been updated.
In a forest grove not far from the nation's capital, several dozen men and women gather. As the light fades, they enact a ritual over a century old but as fresh and searing as the flame they ignite.
A cross, on fire.
They call themselves "the invisible empire" for a reason: They thrive in secrecy, almost never permitting outsiders in.
Who are they?
"You don't know who I am," one man said. "You could think the world of me, and yet if you see me in this hood and knew who I was, your whole thoughts could change."
"I've been a fireman, I've been in the Navy," said another.
The people wearing these robes walk among us. Yet together, as they were this summer in Martinsville, Va., they are the Ku Klux Klan.
"Klansmen, the fiery cross!" a man shouted.
"For God ... For country ... For race! ... And Klan!" the call and response went.
And just a couple of weeks ago, in Tupelo, Miss., a similar scene transpired.
"Klansmen, we are the only klan in the state of Mississippi!" a man shouted.
"White power!" yelled another.
Over the past four months, "Nightline" has been granted rare access to the Klan -- its rituals, its members, its message of racial segregation, which it spreads with a new urgency.
"We have to protect ourselves, or they will kill us!" Steven Howard, a Klan group leader in Mississippi, said.
To get to the heart of it, we headed south to meet Howard. Along the way, we passed through areas scarred by the battles -- the lynchings and church bombings -- of the civil rights era, making a stop at The Southern Poverty Law Center, which is in Montgomery, Ala. Senior Fellow Mark Potok and his SPLC colleagues have been fighting the KKK in courtrooms and classrooms for decades.
Potok agreed with some Klan members' view that President Obama had been the Klan's most effective recruiting tool in the past four or five years.
"I think there's some truth to that," Potok told "Nightline" co-anchor Cynthia McFadden. "Immediately after Obama was elected, we saw two of the largest hate websites in the country crash."
Potok said they had seen the Klan rise, fall and rise again. By the late 1980s, it had dwindled to a few hundred. But now, the story is very different.
"The Klan and other [similar] groups grew pretty significantly by our account," Potok said. "Six hundred groups in the year 2000 to 1,018 last year."
"And that's not the half of it," he continued. "Militia groups have come back, and have come back with a force that is amazing."
We followed the aforementioned Klan group leader, Steven Howard, 31, to a remote spot with a trailer next to the woods. Cell phone service was spotty. Howard's wife, Nicole, was cooking and serving food, creating an atmosphere reminiscent of a regular Saturday-night barbecue. The Howards' 11-year-old daughter was there.
"You cannot get any better southern dish than what you get here!" Howard said.
When the interview began, the regular feeling ended.
"Black people and white people are nowhere related," Howard said. "In my opinion, black people evolved from animals. That's what I think they evolved from: apes."