Returning from a combat mission in the Zephyr, the Roughnecks are re-routed to an ice asteroid to join scientists from another ship, the Sequoia, in a quest for a bio-weapon against the bugs. But the ship crashes, badly damaged, and its communications system is down. Three teams are sent out to locate the Sequoia, but all of them encounter new problems.

Rico, still in the base hospital, reports hearing strange noises, convinced that Bugs are about to attack, leading his doctor to contemplate giving Rico a Section 8 discharge for PTSD. Meanwhile, the Roughnecks seem to be constantly at each other's throats as they map the strange tunnels out in the jungles of Tesca Nemerosa, and  It soon becomes clear that Rico was the "glue" that held the squad together.

Rico lies in the Zegema Beach Hospital, hovering in a coma between life and death as a monsoon knocks out the power. In his delirium, Rico flashes back to high school with Dizzy, Carl, Carmen and Razak, and basic training with Drill Sergeant Zim.

After Gossard receives a minor injury, Rico is assigned a Marauder suit for their mission upriver to capture a Brain Bug. But what they find is a nursery for new and even more dangerous species. Razak calls in an airstrike, but Rico is separated from the squad and is in its path as his Marauder runs out of power.

As the squad goes on Recon in the Tesca Nemerosan jungle, a giant Spider Bug starts abducting them one by one. Eventually, Rico and T'Phai are left alone and forced to work together, even as T'Phai's malfunctioning powersuit has turned him into a true liability.

Colonel T'Phai, the Skinnie who was partially responsible for Carl's fried brain, is not particularly welcome when he joins the unit just as they're assigned the task of taking Zegema Beach as part of the Tesca Nemerosa campaign.

After clearing a mountain pass of a row of Blaster Bugs, the Roughnecks are able to capture Colonel T'Phai, the leader of the Skinnies. But what Carl finds out in interrogating him is a huge surprise.

While returning from a mission, the Roughnecks are attacked and captured by a contingent of the humanoid Skinnies. Tensions mount in their prison cell, and while Carl and Brutto are being interrogated, the rest of the squad works on an escape plan.

When a Cyborg nicknamed Chas (Cybernetic Humanoid Assault System) is assigned to the Roughnecks, he is befriended by Higgins, who views the robot as a kindred outsider, but Rico is mistrustful.

Razak and Higgins spot a huge Bug migration and call in an air strike, but are trapped in the path of destruction when their skimmer crashes.

Sent to the planet Tophet to determine if it can be used as a waystation, the Roughnecks encounter an indigenous race of humanoids.

The Roughnecks discover the commander of Delta Squad, Lt. Ross, wandering around on Hydora with his long-term memory wiped out and his entire squad missing.

The Roughnecks return to Hydora to locate two squads that have seemingly vanished into thin air.

The Roughnecks are sent to destroy a rippler nest on Hydora.
 

Rico is reunited with Carmen when what starts as a simple retrieval mission on Hydora develops into a full blown battle with huge numbers of a aggressive new strain of ripplers known as kamikazes.

When a transport bug is followed from Pluto to the planet Hydora, the Roughnecks are ordered to determine if it could be the bug home world.

When the Roughnecks are sent underground to locate the tunnel with the bug army's hatchery, Dizzy suffers from an attack of claustrophobia.

The Roughnecks must rescue a demolition squad trapped in a canyon by flying warrior bugs. Meanwhile, Rico must train a reporter so that he can defend himself in combat.

The Roughnecks are sent on a special mission behind enemy lines to help an intelligence officer bring back a live plasma bug.

Pilots Carmen and Zander have to be rescued when their ship is shot down by the plasma bugs.

When Rico, Flores and Jenkins arrive on Pluto they discover that research ouposts are being threatened by dangerous plasma-shooting alien bugs.