Damning evidence reveals drug lab chemist Sonja Farak's addictions. A scandal erupts, raising questions for the thousands of defendants in her cases.

Top state lab chemist Annie Dookhan falls from grace over brazen misconduct and unsettling emails with prosecutors. Farak's trial begins.

Farak's disturbing confessions lay bare a broken system. Dookhan takes the fall in court, but suspicions of a high-level cover-up grow louder.

The ACLU and dogged defense lawyers fight for justice in the tainted cases as officials and the public absorb the fallout's staggering scale.