Don't worry, Burgess hasn't left Chicago Pd (but here's why she was Mia in the season 12 premiere)

A new season of Chicago Pd premiered on September 25, as NBC's hit crime drama returned with the first new episode of season 12. The episode marked the first episode of the series without Tracy Spiridakos, who left the series at the end of season 11 after eight seasons. Surprisingly, however, Upton wasn't the only character missing from the season 12 premiere, as it was explained at the beginning of the episode that Burgess was out of town.

In a brief, one-shot line, Ruzek reveals that Burgess is in New Orleans for a conference. This line is meant to explain why Marina Squerciati's character is absent from the episode. Although an explanation was provided, her exclusion from the episode understandably caused fans to fear from the start that she had also quietly left the show.