The "Transport" Bug that was found bringing reinforcements and eggs to Pluto is followed back to the watery planet Hydora, where it releases barb-shooting flying bugs of a previously unknown type. Is this the bug home world?

The battle against the Bugs moves to the watery planet Hydora, where Rico and the Roughnecks again come to Carmen's rescue when she is stranded while evacuating wounded.

Searching for the Rippler nest on Hydora, the Roughnecks come under heavy fire and Jenkins is severely wounded by an acid-tipped barb. Can Jenkins survive his wound and can they find the nest?

Trying to locate two missing squads that seem to have vanished into thin air, the Roughnecks find themselves battling giant amphibious beetles.

While trying to find out what happened to Lt. Ross, who was found wandering on Hydora with his memory gone and his entire squad missing, the Roughnecks are captured by the Bugs.