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.

Emotions run high after despicable fake news 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 to the fore. A mugging opens Kirkman's eyes to the realities of life in the capital.

A stray Russian bomber jeopardizes Seattle, Mars crusades against a drug company, and an event from Aaron's childhood vexes Kirkman's campaign.

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

On election day, Kirkman turns to his therapist to assuage his conscience about the events -- and his own decisions -- of the momentous prior 36 hours.