When post-apocalyptic comic book adaptation "The Walking Dead" made history by winning the entire 18-49 demographic during the first half of season 3, it not only humbled DISH Network but brought AMC Networks (NASDAQ:AMCX) to new highs.

Sunday's second-half premiere brought yet another cable record: 12.3 million viewers overall and 7.7 million in the sought-after 18-49 demographic. Despite this, AMC shares sank with the broader market Monday and ended off 0.29%.

What gives? Investors may be concerned that showrunner Glen Mazzara is leaving when season 3 concludes several weeks from now. Supervising producer Scott Gimple has been tapped to replace him once season 4 begins in the fall.

The handoff has to go well. As diverse as its network properties are, including ratings winners "Breaking Bad" and "Mad Men," it's "The Walking Dead" that AMC owns directly thanks to a deal with co-creator Robert Kirkman's Skybound comic book imprint. No other studio is involved. By contrast, Lions Gate Entertainment (NYSE:LGF-A) produces "Mad Men" in conjunction with AMC.

Investors betting on AMC at current prices are, in effect, betting that "The Walking Dead" will continue to be every bit the hit it is now. Is that a reasonable assumption? I address this question and more in the video below. Please watch, and then be sure to leave a comment to let us know what you think.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.