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.

Anna Hopkins, Bahia Watson, Chad L. Coleman, Frankie Faison, George Tchortov, Jacob Mundell, Josë Zúñiga, Lara Jean Chorostecki, Michael Irby, Nazneen Contractor, Sandrine Holt, Stacey Roca, Tim DeKay