Texas responders run point in a massive multiple car collision; a combative addict and an overdose gone wrong offer challenges in Yonkers, N.Y.; Arizona responders do everything they can to avoid delivering a baby in the back of their ambulance.

Lacey and Stacey restrain a patient suffering from hallucinations after a drug overdose; a man calls 911 to save his wife from cardiac arrest; Alex and Jamal must determine what drug caused a woman to go unresponsive before her heart stops beating.

Alex and Jamal respond to a call for a man with a broken ankle who fell from a fire escape; Steven and Sam are called to a structure fire and must search inside for possible victims; a call for a patient with back pain takes an emotional turn.

In Austin, Texas, Luddy and Finch practice parking-lot medicine when they respond to a heroin overdose; Niki and Nicole help a woman suffering emotional trauma in Baton Rouge, La.; Yonkers, N.Y., medic Alex reveals a sobering truth about her past.

In Austin, Texas, Kim and Audrey can't treat the victim of a gunshot wound until the gunman is apprehended; in Yonkers, N.Y., Cunningham and Ariel answer a call that hits close to home; Niki and Nicole try to save the life of a fellow service member.

An overdose patient wakes up swinging in the back of Meghan and Dee's ambulance; Ariel and Cunningham rush to the scene of a flaming motorcycle wreck; Kim and Audrey hope to find a missing truck driver at the bottom of a ravine.