9-1-1: Lone Star's explosive trailer leaves fans with major concern for 'Tarlos'

9-1-1: Lone Star is back with an explosive season premiere. Teasing the "highest stakes yet," FOX has released a new trailer for series five, but it's sparked concern among fans.

This time around, Captain Owen Strand and his team are first on the scene of a devastating train crash, but it gets worse. Among the wreckage, a huge tank of chlorine gas threatens to send a poisonous cloud across Austin, Texas.

Sending fans into meltdown, several took to the comments on Instagram, concerned for the fate of fan favourite couple, TK and Owen. "Please don't let my Tarlos boys get hurt," replied one. "Great, we can finally see TK's clear face, now where is Carlos?" asked another. "I feel like we will get TK in the ICU again," noted a third.

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TK and Carlos, who finally got their fairytale wedding in the season four finale, are in for some serious drama. According to the latest synopsis, Carlos and TK's marriage will be "put to the test when Carlos becomes obsessed with solving his father's murder."

Posing further obstacles, TK will also encounter "someone from his past that could change his and Carlos' lives forever."

Ahead of the season five premiere, Rob Lowe – aka Owen Strand – has spoken about the show's train crash storyline, which will take up two episodes.

"Well, just the scale and spectacle of the train derailment and the arduousness of shooting it. I mean, I love it. I find it really challenging. I love the challenge of it, but it is a brutal, backbreaking grind and I'm like, 'Yeah, I can do that. Let's go. I turn 60, let's [expletive] go.'

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"I love the results of it," he continued. "I love how big it looks. It looks like a movie. Yeah, I think people are going to be blown away."

Consisting of 12 episodes, season five is slated to cause a divide at the 126. The logline also teases Judd's exit to take care of his son, which forces Owen to search for a new lieutenant – a matter further complicated when Marjan and Paul both apply.

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As for Tommy, while the character hopes to move forward in her relationship with Pastor Trevor, the road to happiness isn't smooth sailing.

While fans are excited for the next series, missing from the episodes will be Sierra McClain, aka Grace Ryder. Details regarding her exit remain limited, however, Deadline states that her departure follows some "cast renegotiation drama".