Naomi makes a desperate attempt to save her son from Marco. On the Roci, Holden battles for the last sample of protomolecule.

Naomi comes face to face with Filip. Holden and Fred turn the tables. Avasarala closes in on Marco’s plot.

Holden and Fred deal with infiltrators on Tycho. Drummer’s past comes back to haunt her. Amos returns to Baltimore. Alex and Bobbie’s investigation on Mars leads to rogue soldiers.