David Duprey/AP

Nik Wallenda looks at the tightrope cable in Niagara Falls, Canada on Wednesday.

As if there wasn't enough drama in walking across Niagra Falls on 2-inch-wide cable, Nik Wallenda has added a bit of last-minute mystery to his audacious attempt.

If you're not familiar with the story, Wallenda is trying to become the first person to walk across Niagra Falls on a tightrope. Here's ABC with a the details:

"Others have crossed the Niagara River itself, but never over the falls. Wallenda said that tonight's feat will be the fulfillment of a lifelong dream as well as a chance to honor his great-grandfather, legendary funambilist Karl Wallenda, who died after falling from a tightrope in Puerto Rico in 1978.

"Wallenda, 33, has called his great-grandfather his "biggest inspiration" and said he will be thinking of him during the stunt. The 1,500-foot walk between Goat Island in the U.S. side to Table Rock in Canada will be fraught with unforgiving natural conditions: blinding mist and drafts created by the force of the waterfalls crashing down on the Niagara River.

"Those obstacles notwithstanding, Wallenda told reporters Thursday that he hopes the walk will be "peaceful and relaxing."

Wallenda is scheduled to begin his walk at 10:15 p.m. ET. ABC is airing it live and it will stream beginning at 8 p.m. here.

But there is one question that is still up in the air: Will Wallenda wear a safety harness?

The Los Angeles Times reports that ABC has threatened to kill the broadcast if he goes untethered.

Wallenda told the paper that he's used to walking without a harness, so doing this with one might make things more dangerous.

"The truth is, mentally it might add to it," Wallenda said.

So will he, or won't he?