9-1-1: Lone Star drops trailer for rumored final season (and it's thrilling)

9-1-1: Lone Star is in a tough spot. All signs point to the show being canceled after its upcoming season. Rob Lowe, the anchor of the show's ensemble, said as much during a recent interview. He was also adamant, however, that the fifth season will be the best yet.

Now that we've seen the trailer, we understand why. 9-1-1: Lone Star is really going for it in the new season, thanks to an especially deadly emergency. It appears as though the crew of 126 Fire Dept. will have to contend with a derailed train, and the "poison cloud of death" that gets released after it derails.

The show introduces its deadliest threat yet

The word choice may sound dramatic, but that's quite literally what the crew refers to it as "poison cloud of death." When the professionals start dishing out hyperbole as earnest description, that's when you know things are serious. There are a few brief shots in the teaser that show the effects of the cloud. One poor civilian appears to be bleeding from her eyes.

Lowe's character declaring that "we have a problem" is putting it mildly. The fact that the show may not be coming back for another season also ratchets up the tension in terms of mortality. We see a pair of first responders laying amidst the rubble of a train car explosion. In different circumstances, we'd be confident they make it out alive. Here, though, we aren't so sure.

Season 5 will likely mark the end of 9-1-1: Lone Star

The derailed train appears to be the most difficult emergency the 9-1-1: Lone Star team have had to contend with to date, as evidenced by the fact that most of the team, including Owen Strand (Lowe) and Tommy Vega (Gina Torres) look completely unsure as to what to do next.

It's jarring, but it's also exciting. It really looks like the cast and crew put their best foot forward, and are poised to give us a sendoff we won't soon forget. 9-1-1: Lone Star returns to FOX on September 23.