Intermittent flashbacks reveal Martians desired freedom from Earth for nearly 140 years. That's when a Martian-born fusion engineer developed a game-changing drive that allowed humans to use spacecraft to "colonize the asteroid belt and remake the solar system." 

The engineer, Solomon Epstein, says Martians were ready to govern themselves, but Earth wouldn't allow it.

In the present, the Rocinante crew and the Belters on Tycho Station mourn and hail the recently departed (we're 99.9 percent sure of it) Joe Miller.

He saved Earth by convincing Julie Mao (or her consciousness) to steer Eros, the deadly, Protomolecule-infected asteroid, away from Earth and crash on Venus' surface.

Holden and Naomi tell Amos they're sleeping together. It seemed at times like Amos and Naomi were a couple.

But when Amos doesn't go ballistic and instead razzes Alex about losing their bet as to whether Holden and Naomi were involved, it's clear Amos and Naomi were really "friends with benefits."

While neither Earth nor Mars governments know the origin of Protomolecule, an Earth scientist tells U.N. deputy undersecretary Chrisjen Avasarala he thinks its alien. He lobbies her to go to Venus on Earth's behalf, to investigate the Eros crash site.

Fred Johnson tells the Roci crew that Tycho Station techs successfully overrode and hauled in 150 nukes Earth fired at Eros. He says he'll use them as leverage to help protect Belters from Martian and Earth threats.

On an agro station on the Ganymede moon, both U.N. soldiers and Martian marines are separately  attacked by a ship of unknown origin. The Martian ship, the Scirroco, is destroyed and the Marines are killed.

Only Martian marine Bobbie Draper remains alive — barely. She lies wounded on the surface, with a being of an unknown species menacingly towering over her.