How safe are we from the outbreak of nuclear war?

British director Lucy Walker gives a chilling answer in her new documentary, "Countdown to Zero." We're all living on borrowed time.

Walker's eye-opener traces the history of the bomb, naming all the countries that possess nuclear capabilities and those nations racing to join them.

"Countdown" also outlines how failed diplomacy, an act of terrorism or a simple accident could unleash WWIII.

"We live in a much scarier world today, with less secure nuclear arsenals than in the Cold War days," Walker told CTV.ca.

"That's why I wanted to make this film, before more countries feel threatened by a nuclear-armed Iran and before the technology becomes so widely available that it's impossible to put the genie back in the bottle," she said.

Narrated by Gary Oldman, "Countdown" wields more explosions and annihilation scenarios than any Hollywood disaster flick.

Colossal mushroom clouds devour the skies over New Mexico, where America first tested the atomic bomb in 1945.

Words like "madness," "miscalculation," "accident," and "sword of Damocles" flash over the screen.

Scientists and politicians like Tony Blair and Mikhail Gorbachev discuss how unfriendly powers could build, buy or steal a bomb.

As one specialist says, "One day somebody's going to make a mistake and we're all going to suffer for it."

Bombs for sale

"Many people I filmed on the street, particularly Americans, were in denial," said Walker. "More Americans believe that aliens will land here before nuclear war happens," she added with a laugh.

But Walker doesn't blame these ordinary Joes.

"It's hard to wrap your brain around something that is so big and deadly," said Walker. "People assume that getting and using a nuclear weapon must be too difficult to pull off. That's where they're wrong."

In fact, "Countdown's" most unsettling jolts come courtesy of two Russian workers.

These men tried to steal and sell highly-enriched uranium, the key component in building a nuclear weapon.

Their motivation?

"I like Americanski cars," said one of the captured thieves.

"I needed the money," said another thwarted criminal.

Some traffickers get caught. Others do not.

But if bumbling novices can get this far, imagine what an organized government or terrorist group could do.

"Access to this stuff is easier to come by than people think," said Walker, who directed "Blindsight" and "Devil's Playground."

Even smuggling uranium seems laughably simple.

"I'd smuggle it in a truck load of kitty litter. No one would ever find it," said one expert.

Another said: "Stash a tiny lump of uranium in a lead pipe to hide the radiation from any border scanners. Then mix it in with everyday objects and smuggle away."

Countdown to zero nuclear arms

What really rattles the nerves here, however, is "Countdown's" account of how close we've come to nuclear disaster.

In 1995, for example, the Americans fired a rocket into the sky to study the aurora borealis.

That innocent test was interpreted by Moscow as a U.S. attack.

If Russian President Boris Yeltsin had not dismissed this as a mistake, a full-scale nuclear attack would have been launched against the U.S. in as little as 28 minutes -- and all because of human error.

"He wasn't drunk," said Joseph Cirincione of the Ploughshares Fund, San Francisco's anti-nuclear, biological or chemical weapons foundation.

Cirincione's black humour earns laughs. But the world's fate could have been decided by one man who acted imprudently.

If that doesn't scare the crap out of you, nothing will.

Great cinematography and a score buoyed by rock numbers like Pearl Jam's closing-credit song, "The Fixer," add to "Countdown's" power.

The film's call for hope also hits home.

"This is an exciting moment in our history," said Walker.

"Once there were more than 60,000 nuclear weapons in the world. Now there are 23,000. That decline is good news. It points to enlightened leadership in the world today that could affect positive changes," she said.

"Countdown's" experts and citizens applaud such change.

"None. Zero. No more nuclear weapons," they tell us.

"This is the way to a safer world," said Walker. "I want people to be reminded of that, and where we'll end up if we don't wakeup."