The Valley Forge is enroute to their next campaign, a long trip. The Roughnecks drew the watch as most of the ship's crew is in stasis. Doc is suddenly attacked by Zander who has mutated into a new form of Bug. Zander escapes and runs amok in the ship, letting samples of other Bug types free to keep the Roughnecks busy whilst it heads for the bridge. There it captures Carmen and the Commander and, to stop the Roughnecks from interfering, kills power to the stasis tubes. Gossard manages to restore power to the tubes whilst Rico and Brutto go outside the Valley Forge to the emergency air lock on the bridge. As they enter the Sander Bug notices them and closes the door trapping Brutto in the process and damaging his legs. The rest of the team arrive and Zander escapes in a life-pod to the planet he was trying to crash the Valley Forge onto. Carmen manages to avoid the crash causing the Commander to withdraw earlier comments about automated pilots. The planet is t

S.I.C.O.N. prepares for the D-Day invasion of the bug home planet of Klendathu. During the build-up Flores gets an M.I.A. notice from telling her. that her brother, Eddie is MIA - presumed dead in a retrieval ship crash. She is badly shaken by this bombshell and her performance as a trooper is severely affected. The Roughnecks land in an area deemed uninhabited by Intel, as usual Intel get it wrong and the meet stiff opposition.

Flores hesitates in the DZ and Rico who's been kicked up to Sergeant to replace Brutto is worried as Lt Razak has left it to him to decide whether she is now a liability. Rico is torn and leaves Flores in charge of a group of wounded troopers from other squads whilst the Roughnecks carry on the fight. As they get bogged down in the fighting Flores is brought back to reality by the will to fight of an injured trooper from another squad. She is able to surprise the Bugs from behind and save the Roughnecks. Later she meets another trooper who

Higgins is on guard duty at a camp on Klendathu. Whilst in front of the gates he sees a trooper staggering along. As he talks to the trooper a new type of Bug, hence known as an Impostor Bug, bursts out of the suit. The Impostor is a Bug that approximates the size and shape of a human and is able to fit inside stolen power suits. As such they present a major threat to the security of S.I.C.O.N. forces. The troopers manage to kill the bug but not before it manages to drop Lt Razak and knock his helmet off. After the attack, the Roughnecks are ordered to rescue the crew of a downed transport ship. When they get to the crashed ships location they discover that the crew have been captured by Bugs. As the squad track them Bugs back to their nest Lt Razak collapses - it seems he has been infected by spores carried by the Impostor Bug. Doc and Flores go to find the fungus responsible so Doc can synthesise an antidote whilst the rest of the squad keep tracking the Bugs.

The Roughnecks are dug in on Klendathu and are facing an inevitable Bug attack. High Command order them to hold the position at all costs. Higgins finds an unfinished letter home an anonymous trooper had begun but not finished. This gives him the idea of taping a series of ""Goodbyes"" from the rest of the squad to the folks back home - just in case. Through out the night the troopers individually record messages to their families on Earth. At day break the Bugs attack but the Troopers manage to hold them off just long enough for a major air strike to hit the Bugs. As they prepare for retrieval Higgins asks Lt Razak if he wants to tape a message to his family - Razak points him at the squad and tells him that these are his family.

Lt Razak is called to a mission briefing to find it being given by Sky Marshall Sanchez himself. The Sky Marshall tells the assembled officers about the of the Bug Queen. He then assigns Alpha and Echo squads the mission of locating and destroying the Queen. One bit of seemingly good news is the return of Carl to the squad. But the Roughnecks are dismayed to find an apparent change in his personality. Carl guides the roughnecks to the queens lair but is captured by Bugs enroute losing his helmet in the process. The Roughnecks find the Queen but she is holding Carl as a shield and Rico is unable to pull the trigger on his friend. In the fire fight the Queen drops Carl and Rico returns his helmet. The squad give chase to the Queen but are unable to stop her escaping on a Transport Bug - enroute to Earth!!!!