If an opiate antagonist blocks the effect of opiates, can the drug Naloxone protect drug mules from overdose?

I was watching the movie "Maria Full of Grace" and one of the body packing mules has a balloon burst and kill her. If she had an adequate dose of Narcan, would the effect of a large dose of heroin be blocked? Since there's no "high" from Narcan, wouldn't that safeguard mules?