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

A heated debate over child marriage causes tension between Kirkman's staff. Opioid addiction hits home for Mars and 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, while Wells and Eli track a bioterrorist.

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

Emotions run high after a despicable fake news story goes viral. Isabel makes waves with a controversial appeal and Wells finds a clue pointing to conspiracy.

A dying Guatemalan child in a Texas hospital brings immigration up front. A mugging opens Kirkman's eyes to the reality of life in the capital.

A stray Russian bomber threatens Seattle, Mars crusades against a drug company. An event from Aaron's childhood rings trouble to Kirkman's campaign.

Kirkman enacts a frantic hunt for the bioterrorist. Lorraine plays hardball and pushes the opioid epidemic into the campaign.

Behind in the polls, Kirkman weighs forcing the FBI's hand over the bioterrorism plot. Meanwhile, Emily struggles with her mother's last wishes.

On election day, Kirkman turns to his therapist to relieve his conscience about the events and own decisions he made 36 hours ago.