Coulson's team boards a mystery train in Episode 13 of Agents of S.H.I.E.L.D. Image source: Disney/Marvel

In what many viewers hope marks the beginning of a much more Marvel-ous run for Disney (DIS 0.55%) Marvel's Agents of S.H.I.E.L.D., ABC's most popular new series, returns tonight with an all-new episode.

Agents of S.H.I.E.L.D.'s creators have already promised the show will incorporate more pervasive Marvel-centric themes going forward, including a recently revealed integral role for Thor: The Dark World's Jaimie Alexander as Lady Sif in episode 15. If that weren't enough, comic fans are brimming with excitement as Bill Paxton will soon join the show for a minimum four-episode arc as roughneck Agent John Garrett.

And based on the preview clip Marvel provided during the end credits a few weeks ago, not only will fans be treated to a guest appearance from comic book legend Stan Lee tonight, but things are also about to take a permanent turn for the worse for one of the show's cast members:

 

Now greater questions remain: Will this "astonishing, series-changing final act" actually mean the killing off of a key cast member before Agents of S.H.I.E.L.D. concludes its first season? Or is Marvel instead simply ending the role of one of the show's less-crucial supporting cast members?

In either case -- and putting aside the fact Coulson's resurrection proves the show could theoretically revive anyone if they so choose -- Agents of S.H.I.E.L.D. is treading thin ice with a teaser like this one. After all, to end the role of any of the show's primary players could cause loyal fans to revolt in objection. And viewers could be discouraged from watching future episodes if the event really isn't all that "astonishing."

Here's what they're trying to accomplish

The end goal for Disney, of course, is to push more curious viewers off the fence and into Agents of S.H.I.E.L.D.'s gradually increasing fan base.

And while I'd argue Agents of S.H.I.E.L.D. doesn't necessarily need the boost, you won't find Disney and ABC complaining if their antics entice a few more of CBS' (PARA -4.38%) live NCIS viewers to jump ship.

In Agents of S.H.I.E.L.D.'s most recent new episode, for example, Agents of S.H.I.E.L.D. held steady with 6.37 million live viewers, earning a 2.2 rating in the key adult 18-49 demographic. Once again, though, that was still "only" good enough for second place to CBS' perennial ratings winner, which scored a 3.0 rating with a staggering 19.72 million live viewers.

But Agents of S.H.I.E.L.D. continued to win key valuable groups, notably leading NCIS by 50% for men 18-34, good for the top men's spot for its 12th consecutive first-run airing.

Episode 12 also gained 5% in the women's 18-49 demographic, marking the show's best female turnout in more than two months. Finally, Agents of S.H.I.E.L.D. remains TV's the top-rated live broadcast program overall with teens age 12-17, and is still Tuesday's number one show this season in adults 18-49 after accounting for the most recent Live + 7 day ratings.

And even if we ignore Agents of S.H.I.E.L.D.'s ratings performance to date, we also need to keep in mind Disney has granted it relatively unrestricted reign on literally thousands of characters in the Marvel Universe -- so long as the use of those characters meshes with the shared storylines being developed in its wildly popular big-screen counterparts.

In the end, and regardless of whether a key cast member departs tonight, that's why I'm convinced Agents of S.H.I.E.L.D. will be just fine.