The secret of the asteroid becomes public following a nuclear incident, setting the world on a dangerous course.

Darius and Grace must forge an emotional détente in order to get international cooperation.

Loyalties are tested when Grace is asked to lie under oath. Jonathan Silverman guest stars.

Grace embarks on a dangerous mission, and Liam and Darius' relationship is tested.

Grace forges a dangerous alliance with Claire's brother, Alonzo (Ashley Thomas).

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

Darius vows revenge on the hacktivist group Re/Syst, no matter what the cost.

Desperate to defuse a nuclear standoff, Liam receives help from an unlikely source.

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

Darius forms a dangerous alliance in order to destroy the dark money forces of Q17.

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

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

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