Since her son has been healed and changed by the Terrians, Devon has been worried she’s going to lose him to them. This episode is about this. Also, Alonso does some stuff.
There are two moons around G889 and it seems like they spin in opposing directions. When they cross, it is a special time the Terrians call Moon Cross. This is a time of mystical strangeness, including the Terrians being able to “die” by becoming one with the planet. Presumably Moon Cross is also why the crew encounter Actual Ghosts! The spirits of the dead speaking to the living is a thing that can happen on Earth 2!
Anyway, winter is approaching and our explorers need to find a place to set up camp. Uly, via his connection to the Terrians, leads them to a nice greenhouse that has apparently been there for fifteen or so years. Uly calls it “Mary’s garden” and it’s a perfect place to spend the winter, if it weren’t for the ghosts. It also allows Devon to face her fears about losing her son to the Terrians when they find Mary, a human who was taken by a Terrian tribe when she was a child and who now considers herself a member of that tribe, barely remembering humanity at all. It turns out that the Terrians who killed Mary’s parents are now outcasts from the tribe, denied the opportunity to die during Moon Cross. There’s a halfhearted attempt to reconnect Mary to her humanity (Bess gives her a bubble bath) but it doesn’t go well. In the end, it looks like the Terrians are going to take Uly, but actually Uly is in some sort of Moon Cross Trance and he tells the Terrians to let the outcasts die now, so there can be peace (he’s getting closer to that dream he had about being a Terrian prince or whatever). In the end, Mary goes back with the tribe that raised her after her parents died, Uly doesn’t actually remember what happened during the trance (but he does get to keep a Terrian lighting staff which will surely be important in the future), and Devon feels a little better about things for the time being.
Now, hit me with the bullet points that instead of bullet points I put in numbered sentences in a paragraph for some reason: 1) Alonso narrates the episode and there’s considerably more narration than usual. I can’t help but wonder if they assumed the audience wouldn’t know what was going on with a lot of the Terrian stuff, so they added the narration to spell it out. 2) Mary’s parents were part of some “radical biologist” group that got put into the penal colony on the planet. When Yale tries to use his computer brain to find out more, it prevents him from doing so, which he thinks may be a sign that it is connected to his pre-wash identity, which is confirmed when he remembers some facts about it from actual memory, instead of via his computer. 3) The moons are one of the special effects on the show that don’t impress me. Stick to puppet aliens, please. (Actually, I’m surprised we’ve not had a return of the little monkeytype alien from the pilot.) 4) There are hits of intimacy between Mary and Alonso, which don’t actually go anywhere (as well they should not), but they do make Julia jealous.