Now running for office for the first time, Kirkman and his nascent campaign stumble out of the gate. Wells gets a critical reassignment.

A heated debate over child marriage roils Kirkman's staff. Opioid addiction hits home for Mars. A biohacker turns Wells onto a chilling new threat.

A political attack on Kirkman puts privacy and transgender rights in the spotlight. Aaron weighs a major decision. Wells and Eli track a bioterrorist.

Aaron's heritage and a widespread teachers' strike become polarizing issues, and Wells discovers a sinister pattern in a flu outbreak.