Jesse Spencer, Taylor Kinney Jesse Spencer, Taylor Kinney

Two of Firehouse 51's own went missing in the final moments of Chicago Fire 's fall finale, but that doesn't mean the rest of the team will get to take a breather from their day jobs to look for Mills and Brett.

In this exclusive sneak peek from Tuesday's new episode (10/9c, NBC), the rest of the squad doesn't get called to just any fire - they get must report to the scene of a fire at a storage unit facility. "Storage units are the pits," Herrmann ( David Eigenberg ) tells Dawson (Monica Raymund ). "You got to bust into each unit and worse, you got no idea what you're going to find behind each door."

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Sure enough, what Severide ( Taylor Kinney ) finds behind one of the doors knocks him out. Check out the exclusive sneak peek below to see the mysterious cause.

Chicago Fire airs Tuesdays at 10/9c on NBC.