The 911 system functions as a sort of promise: Call for help and someone will be there to respond quickly. But in many American cities, it’s a broken promise.

Thanks in part to a widespread understaffing crisis across 911 dispatch centers, hundreds of thousands of callers are left waiting on hold during their most harrowing moments every year.

Reporter Byard Duncan has spent more than a year reporting on America’s flailing 911 system and what it might take to fix it. This week on Reveal, in partnership with Type Investigations, he traces the issue from California to Wisconsin and a final stop on Capitol Hill.