One last mystery holds the key to saving the world, and Grace must choose how she spends her final days.

The government's final plans for a doomsday scenario set in motion a surprising chain of events for Grace, Darius and Harris.

A stand-off at the COPE compound leads to tragic results.

Darius forms a dangerous alliance in order to destroy the dark money forces of Q17. Also, Grace takes action when surprising news jolts her world.

Darius, Grace and Harris uncover the darkest secret yet, and Liam reconnects with Jillian.

Desperate to defuse a nuclear standoff, Liam receives help from an unlikely source. Also, with Darius missing, Harris and Grace take matters into their own hands.

Darius vows revenge on the hacktivist group Re/Syst, no matter what the cost. Also, Harris discovers a dark secret and Grace reveals one of her own.

Darius and Grace's relationship is tested, and President Mackenzie attempts to bring the fractured country together while the hacktivist group Re/Syst issues a deadly edict.

Grace forges a dangerous alliance with Claire's brother, Alonzo. Also, Harris and Darius must work together to face down Bennett's forces.

Harris, Grace and Darius must topple the illegitimate government, and Darius makes final plans for the ark.

To prove to Harris and Grace that he's not a traitor, Darius must reveal a closely guarded secret; Liam helps Jillian adjust to her new job at Tanz.