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

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

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

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