Why was Gamma called back to The Sheridan, anyway?

Heaven - Season Five: War

War Episode 13

Kate and Daniel remain exiled in the new world they created, with the need to build an army to save Heaven. But the allies they need may not be willing participants, as they're trapped gods who blame Kate and Daniel for their imprisonment. As the dark power that traps Heaven begins to seep into Kate and Daniel's new world, they face new enemies and learn about a very old obstacle that blocks them from their goal.

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Heaven - Season Five: War