Holden tries to convince Fred Johnson to destroy the last sample of protomolecule. Naomi gets an important lead to her son. On Luna, Avasarala begins to hunt for Marco Inaros.

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.

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

Marco's grand plan shocks Earth, Mars and the Belt.

Holden and the Roci face off against Marco's forces and Drummer, while Alex and Bobbie attempt a dangerous rescue of Naomi, and the balance of power in the Solar System shifts.