Oliver Stark, who portrays Buck on “9-1-1,” added to fan theories when he posted a picture of himself hanging out with the cast of “9-1-1: Nashville” on his Instagram story Oct. 6 and encouraged fans to watch the spinoff. McVey reshared the photo on his Instagram story and added, “Come back soon brotha.”

9-1-1: Nashville kicks off in classic franchise fashion: with the tease of a major emergency. During a Kane Brown concert, after part of the stage collapses, a tornado approaches. Then, flashback to two weeks earlier, when Captain Don Hart ( Chris O’Donnell) introduces his son Ryan ( Michael Provost) to his other son Blue ( Hunter McVey ).