On the eve of the worst crisis in human history, Congresswoman Jennifer Brown clashes with the President.

After a mass casualty event wipes out every creature with a Y chromosome, President Jennifer Brown responds to the crisis; Yorick fears he may be the only survivor.

The president's daughter, Kimberly, circles Jennifer's secret; Nora Brady and her daughter, Mack, say goodbye to home.

On Jennifer's orders, Yorick and Agent 355 search for a geneticist who can unravel the mystery of how he survived; Hero and Sam encounter a dangerous group of women.

Yorick and Agent 355 search for Dr Allison Mann in war-torn Boston; back in Washington, DC, Jennifer hides the truth about Yorick from her political rivals.

Yorick, Agent 355, and Dr Mann hit a snag on their way to San Francisco, which leads to some unexpected results.