Shock waves hit a Salvare struggling in the aftermath of an epic act of destruction. Nike questions William's judgement as Erik looks to the Achaia.

Venturing into the ring to negotiate with the Achaia, Niko sees the unimaginable. Cas risks everything by sending Iara on a mission. Jana stuns Erik.

Left behind but holding on, Niko and Cas each tangle with the Achaia in their own way. At the Salvare, the crew uncovers a key alien vulnerability.

Under suspicion for severing a lifeline, Iara now finds her life on the line. William discovers a surprise within. A habitable planet calls to Cas.

The new planet holds promise - and unexpected threats in the brush. The tables turn as Richard reaches out to Iara. The Achaia open up to Erik.

Alone at last, or not? Salvare's team faces a rough ride home - and a cautious reentry. Elsewhere, Erik tests Achaian tech, then asks for a favor.

Giving up isn't an option: Nike hatches a plan and spars with Richard. The chase is on when the crew tries to stand strong, and noises rattle nerves.

In a flash, Niko and Richard's world takes a terrifying turn as they wake up in a cold, cruel trap. On Earth, the team grapples with memory gaps.

Eager to go home by any means necessary, Niko and Richard head to a planet with an artifact. Erik and Cas go undercover, and William brokers a deal.

As the Achaia close in, the crew moves quickly to create a new weapon and save Earth. The time has come for the heroic to make the ultimate sacrifice.