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: Niko 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.