TORONTO – Before Matthew McConaughey's character drives through flames to save 23 souls, he has quite the fire to put out on the homefront.

Directed by Paul Greengrass, the thriller "The Lost Bus" (in select theaters Sept. 19 and streaming on Apple TV+ Oct. 3) centers on the true-life heroes of the 2018 Camp Fire, the deadliest wildfire in California's history. McConaughey plays hard-luck bus driver Kevin McKay, who's responsible for getting more than 20 kids and their teacher (America Ferrera) home while also worrying about his teenage son Sean. Early in the movie, they have a serious fight that ends with Sean yelling, "I hate you! I wish you were dead!"

A tearful McConaughey wears so much emotion on his face in that moment, and it's interesting on a whole other dramatic level because Sean is played by the Oscar winner's son Levi, 17, in his film debut. (Another fun fact: McConaughey's mom, Kay, plays Kevin's mother.)

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"I cannot imagine those words ever come outta my son Levi. Not to me," Matthew McConaughey says a day before premiering "Lost Bus" at Toronto Film Festival. "Does the nightmare of that kind of relationship parlayed with the gratitude and thanks that that's not our relationship compound in that moment with Kevin in the hallway? Yeah. That's why the hugs were a little longer after the scenes were done and it was an exhale of, ahh, glad that's not our relationship."