TK gets a huge surprise on his 30th birthday when his stepdad Enzo arrives in Austin along with TK's young half-brother Jonah; Owen's resentment of Enzo turns physical; Tommy is determined to push through her latest crisis; Wyatt attempts to talk-down a suicidal caller and the 126 must perform a dangerous surgery in the field after a man is impaled in a tree.

Owen makes a decision about his future. Tommy receives devastating news. T.K. and Carlos worry about adopting Jonah. Mateo gets his immigration status threatened after an altercation. A doomsday prepper gets trapped in a bomb shelter and The 126 and all of Austin brace for an asteroid crash.

Owen and the 126 deal with the aftermath of the asteroid crash in Austin while an even greater threat looms.