Nineteenth-century spectacle meets 21st-century television on “Megastunts — Highwire Over Niagara Falls — Live!” (8 p.m., ABC).

”Live!” is the most telling word in the title. Not only will ABC broadcast Nik Wallenda’s attempt to walk 1,550 feet on a tightrope suspended 173 feet above the roiling water of Niagara Falls in real time, but there is an implied promise that its cameras will not cut away should the daredevil slip and fall.

The network will apparently tether Wallenda to his wire, and the daredevil has gone public about his unhappiness with his safety belt. But ABC is still banking on folks tuning in to see Wallenda’s old-fashioned “death defying” act.

Few people will come out and say they’re watching this stunt in the hopes of witnessing something go terribly wrong. That would be like saying one attends NASCAR events anticipating a crash. But if you’re completely certain of Wallenda making it without incident, then why watch at all? Why else invest the stunt with so much power? And why set the spectacle at Niagara Falls, a place with a long, sad history of attracting suicides?

That last fact may explain why stunts like Wallenda’s have been outlawed at the falls for the past 125 years. Will ABC be around in the months and years to come when amateurs, imitators and the purely self-destructive try to re-create Wallenda’s antics — without success?

The programming geniuses behind tonight’s spectacle have said that they wanted to reach back to the excitement of Evel Knievel’s televised stunts of the 1970s. But “Megastunts” harks back to rites and rituals far more ancient than that. The crude appeal of “Megastunts” is far closer to the Roman gladiatorial pits than the ancient Greek stage.

It’s an understatement to say that “Megastunts” cheapens TV. It demeans us all.

If viewers have to watch somebody risk death to be stimulated, or distracted from their boredom, then we’ve moved far beyond — or beneath — the realm of entertainment.

“Megastunts” is far closer to the Roman gladiatorial pits than the ancient Greek stage.

Tonight’s other highlights

• A sister vessel founders on “Whale Wars” (8 p.m., Animal Planet).

• Kate mediates a legal tangle in a newsroom on the season finale of “Fairly Legal” (8 p.m., USA).

• The new series “Evil, I” (9 p.m., ID) recounts notorious tales of murder from the killers’ point of view.

• A team of masked burglars may include Travis’ foster brother on “Common Law” (9 p.m., USA).