Dr. TC Callahan (Eoin Macken) is an ex-Army medic who initially exhibits PTSD-type symptoms, having watched his brother die right in front of him on the battlefield.

[3] At a TCA Press Panel, series creators Jeff Judah and Gabe Sachs both said that the new timeslot with such a powerful lead-in was "a really big deal for us.

[6] The role of Landry de la Cruz (portrayed by Daniella Alonso), the lone psychiatrist on the night shift, was scrapped for season 2 amid "changes in the creative direction" of the show.

"[7] On October 30, 2014, it was revealed that Adam Rodríguez would be joining the cast as a recurring character, Dr. Joey Chavez, a newly hired trauma surgeon.

[5] On November 7, 2014, Merle Dandridge was cast for a recurring role of Gwen Gaskin, "a lead paramedic working at San Antonio Memorial Hospital and the best friend of Jill Flint's Dr. Jordan Alexander.