WARNING: If you don't want to know what happened in this episode, don't read this photo recap!
In a flashback to before the Ganymede attack, Dr. Strickland is walking with Mei and another woman, as we saw in the security cam footage. As he passes a plant, he sneakily snaps off a leaf and keeps walking.
Back in the present, the Roci crew (minus Alex) retraces those steps and find the tunnel to the old Ganymede station. Naomi tries to prepare Prax for the worst. He tells her she's never lost a child, but she says she has, and it took her a long time to get over the guilt. Whoa. We just learned Naomi had a child and had to give him up (exact reasons are unknown).
On Earth, Bobbie is getting chewed out by Martens for escaping the embassy. She is demanding the truth about the Protomolecule hybrid she saw on Ganymede. She yells that he lied to her. He yells that she's jeopardized the future of Mars. He also tells her she's no longer a soldier and to prep for the trip home.
On the Arboghast, Janus and Iturbi look on with concern as an MCRN ship continues to shadow them. They also continue to try to drop probes down into the Eros crater on Venus, but the probes' signals all disappear before they reach the surface. Iturbi suggests they break protocol and drop lower before releasing their last two probes, and after some debate, Janus concedes.
Errinwright tells Avasarala he has an idea to leverage Jules-Pierre Mao's family in order to get Mao to make contact. Avasarala tells Errinwright he's going to be a scapegoat at the hearings about the Eros disaster unless they can find Mao. And even if they don't, Errinwright should use the hearings to atone for what he's been part of.
As the Martian drop ship enters Earth's atmosphere to pick up Bobbie and Martens, it suddenly reverses course and returns to space. It seems the UN got wind of an OPA plot to bomb the transport, and Avasarala put a hold on the pickup. So Bobbie and a suspicious Martens return to their quarters.
Alex and the Roci are still hiding out behind one of Jupiter's moons amid a no-fly order. Suddenly, there's an MCRN alert about a ship, the Karakum, that's been granted clearance to land on Ganymede. Alex surmises it's some kind of black-ops deal; he needs to get down to Ganymede first, and he plans a wildly ambitious slingshot-around-a few-moons plan to get the Roci down to the surface without detection.
In another flashback, this time at the beginning of the Ganymede battle, Strickland and the other woman, Umea, bicker about how this field test of theirs has gone horribly wrong and could trigger a war. Mei speaks up and wants her daddy, but Strickland manages to talk sweet to her and give her an injection before leading her along to the next place.
The Roci crew continue to trek through the tunnels as the air cycler shuts down in the station. Prax begins to explain the "cascade effect" like he did to Amos last week, but Amos interrupts with the short version: "Means this station is fucked." Prax spots a vial of Mei's medicine and surmises that Strickland is keeping Mei alive. Holden says they should keep going.
Bobbie requests to see Martens, who is in his room, receiving a message about the Karakum landing on Ganymede to pick up "Caliban." She again demands the truth and then attacks him, angry that her team was killed for a weapons test. She makes him show her proof: Project Caliban was a field test and WAS that protomolecule hybrid that killed her entire crew; he shows her footage from the drone she saw that night. "It was for the good of Mars," he says.
Bobbie knocks Martens out and manages to also knock out a security guard. She makes a run for the perimeter fence around the Martian embassy, but she'll never make it. So she gives herself up…to UN authorities. She's requesting political asylum.
Alex begins his elaborate plan to slingshot around verious moons and land on Ganymede. He's actually doing really well until he almost runs straight into an MCRN ship. He manages to slip behind one of the moons and escape detection.
Bobbie has been brought in to see Avasarala, who jokes about Bobbie creating a diplomatic incident. Bobbie tells Avasarala that she was right - the Protomolecule hybrid is a weapon, and right now it's up for sale, and Mars is in line to buy it. She hands over Martens' information on Project Caliban, and Avasarala sends Cotyar off to analyze it.
The Roci crew has reached a door, and they can hear people on the other side. Prax asks Amos for a gun, which Amos reluctantly hands over. When they bust in, it's the woman Umea and some other scientists eating pizza. Umea wants to talk it out, but Prax spots Mei's backpack and makes a move, so there's a shootout. Umea escapes, and Amos gets shot in the shoulder.
Jules-Pierre Mao has sent Avasarala a message, so her plan to get him to resurface worked. He wants to set up a meeting with Avasarala, but Cotyar thinks it's clearly a trap. Avasarala may well agree, but she's already arranged to meet.
In the aftermath of the grenade, the Roci crew sees that something was able to break out of captivity. A Protomolecule hybrid? Holden sees Umea, mortally wounded, and she tells him they molded the Protomolecule "...in our own image. And there's a lot more where she came from."
Suddenly, Alex shows up outside the air lock. He's here to pick the crew up, but Naomi tells Holden she's staying. She wants to do some good, and helping the Somnambulist to evacuate the survivors on Ganymede is a start. Holden tells her to keep Amos with her, and they kiss goodbye.