When an alien race wipes out the majority of the human population, a group of survivors gather to fight back against a highly intelligent, heavily armed alien force whose purpose on Earth is the biggest mystery of all.

Tom and Hal lead a squad in a search for supplies but are ambushed by a rogue gang led by ex-con John Pope. Pope plans to use the hostages to gain control of the weapons 2nd Mass stockpiled since the invasion began.

The 2nd Mass come face to face with Skitters & Mechs when Tom & Hal lead a mission to rescue Ben and the others. Tom's search for answers to nagging questions could jeopardise the plan presented by Dr. Michael Harris.

Tom and Hal lead a team to find more motorcycles for the 2nd Mass after Pope provides details on where they can be found. Back at base, Dr. Harris and Anne disagree over the best tactic to gather more intelligence.

Hal devises a new plan to save the captured teens but pulling it off could put someone in danger. Following a sudden tragedy, Anne makes a discovery that could mean the difference between the plan's success or failure.

Lt. Terry Clayton of the 7th Mass arrives at 2nd Mass HQ to warn of an impending alien attack. Clayton claims to have a plan to lead the children to safety but his plan is met with strong resistance by the parents.

Hal finds himself having to take control and fight when an unexpected threat presents itself. Anne faces her own problems when Sarah goes into labour as 2nd Mass is being evacuated in anticipation of the alien attack.

Weaver's mental state continues to deteriorate causing trouble for Tom and Hal on a reconnaissance. Pope builds a potent weapon to use against the aliens & Anne makes a shocking discovery performing a Skitter autopsy.

As the assault on the alien base draws closer, tension builds amongst the members of the 2nd Mass. Tom struggles to come to terms with Anne's new discovery about the Skitters.

Tom stays behind to protect the camp and its occupants while the rest of the resistance launch an attack on the alien base. Information regarding the aliens' motives finally comes to light.

Three months after Tom Mason agreed to go with the alien invaders, Weaver is still in command of the 2nd Mass, while Anne continues to serve as medic. Pope has taken command of the Berserkers, a renegade group within the 2nd Mass that Weaver doesn't fully trust.

Tom is still haunted by memories of his time with the aliens, while Pope plants seeds of doubt about him among the group. Ben's hatred for skitters grows and the 2nd Mass scouts locate a bridge that will help them cross the river to safety ahead of an impending attack.

The 2nd Mass moves into an airport hanger but the draughty conditions cause concern for the group's health. The Berserkers hatch a plan to get rid of Tom, and while dealing with a loss of one of its own, the 2nd Mass receives a promise of hope from a mysterious visitor.

While on patrol together, Ben and Hal try to help a young boy and wind up having their bikes stolen. The hunt to recover them leads them to the discovery of something much bigger. Also, Matt is put in danger, and Weaver is reunited with a family member.

A familiar face returns to the 2nd Mass, but his intentions remain unknown. Meanwhile, a skitter is captured and brought back to the camp as a prisoner, and Hal bonds with Maggie as she begins to open up about her past.

Hal stumbles across bodies of de-harnessed kids and finds someone from his past. Tom and Anne grow closer and Weaver's health deteriorates just as Tom discovers he may have been keeping important matters from the group in order to protect them.

Tom captures another hostage and Ben is placed in harm's way by someone who he thought he could trust. When members of the 2nd Mass are trapped in the basement of a building, the situation takes a turn for the worst when they find themselves faced with a new enemy.

The 2nd Mass pushes on to Charleston, but some are still grieving the group's recent losses. Weaver learns more about Tector's background before the invasion, and Matt begins to bond with a harnessed girl who was found recently.

The 2nd Mass meets new faces, while Tom comes across his former mentor and professor Arthur Manchester, but it's difficult to know whom to trust. Maggie begins to realise that Pope may not be sticking with the group very long, and Tector embraces his military past.

When skitters approach the newly combined resistance force, the groups' interaction surprises everyone. Meanwhile, Tom finds out life-changing news just as the 2nd Mass comes face-to-face with their most dangerous threat to date.

Tom has his hands full as the resistance continues to battle the alien invaders. Tom's decision to have the rebel skitters fight alongside humans creates tension and raises suspicions that someone may be feeding secrets to the enemy.

With hostilities escalating between the resistance and the alien invaders, Tom calls on a nuclear specialist to come up with a plan that will strip the aliens of their power. As suspicion continues to mount about a mole, Tom and his leaders make a drastic decision.

The two-year anniversary of the alien invasion is fast approaching as the people of Charleston prepare for another potentially devastating offensive. A sniper attack by an unlikely gunman creates questions and doubts within the new government.

While Hal wrestles with an invasive evil, Ben struggles with his identity and the notion of being human again. Anne, meanwhile, uncovers startling new information that puts everyone in jeopardy.

When a mission goes terribly awry, Tom and Pope must rely on each other to survive. Weaver and company search desperately for two members of the 2nd Mass who have gone missing, and Marina takes matters into her own hands in Charleston, disregarding Tom's authority.

When a mission goes terribly awry, Tom and Pope must rely on each other to survive. Weaver and company search desperately for two members of the 2nd Mass who have gone missing, and Marina takes matters into her own hands in Charleston, disregarding Tom's authority.

The Masons run into trouble when a family of outlaws intercepts their search-and-rescue mission. Looming doubts over the construction of a massive alien weapon ignite a conflict of interests, and an investigation to apprehend a killer on the loose hits a road block.

Things seem much too calm for Tom, making him suspicious of his surroundings. On his way back to Charleston, he makes a number of discoveries, some surprising and others utterly horrifying. Meanwhile, Weaver and Pope butt heads over how to handle the suspected mole.

Tom uncovers confidential intelligence about the heart of the alien operation. As Charleston prepares to mount an offensive against the Espheni, an explosion brings the operation to a halt. The mole's identity is finally uncovered but not before the loss of more blood.

When the 2nd Mass destroys a crucial Espheni base, a relentless enemy is taken down and the Mason family is reunited with those who had been lost; but the arrival of more interstellar players puts the fate of the Earth's remaining survivors in doubt.

On the heels of Tom and Lexi's successful (albeit tragic) mission to destroy the Espheni power core on the moon, Tom's life hangs in the balance as his Beamer drifts into space. Back on Earth, Anne reluctantly helps to lead the 2nd Mass in his absence.

When a surprise Skitter attack leaves the 2nd Mass without food, Maggie, Ben, Pope and Sara go on a dangerous mission hoping to find supplies. Meanwhile, Tom and Anne discover the Espheni have created something part Espheni, part Skitter, part Hornet... and part human.

The 2nd Mass discovers the source for the seemingly endless supply of enemy forces. With the Volm's help, Tom's leadership begins to spread across the world, but closer to home, he makes an agonising decision that risks one of their own with repercussions for all.

Cochise shares troubling news with Anne that will test both her medical and leadership skills, whilst elsewhere Anthony's mental stability and loyalties are brought into question. Meanwhile, a desperate Pope takes things into his own hands.

The 2nd Mass leaves Chinatown en route to what they hope will be the final Espheni battle. Along the way, they encounter a deranged and desperate gunman who takes Weaver hostage. Meanwhile, Tom sets off to rescue Hal from Pope and his dangerous group of survivors.

Injured, Tom takes refuge with a unique family who has distanced themselves from the fight, giving him a glimpse of life without war. Meanwhile, the 2nd Mass locates an Espheni device that could be a linchpin to winning the war... if they can figure out how to use it.

The 2nd Mass arrives at a safe haven - a functional military base run by Weaver's old colleague and flame, Captain Katie Marshall. As the two groups make plans for the final assault on the Espheni, the 2nd Mass begins to realise that things aren't exactly as they seem.

Weaver discovers a shocking truth about an old friend and must decide how to best protect the 2nd Mass. Meanwhile, Maggie and Isabella are forced to work together, whilst the remainder of the 2nd Mass attempts an escape led by Tom.

Tom gains a powerful new weapon against the Espheni. Ben puts his life on the line to extract enemy plans. Pope discovers that Tom is alive, and launches a final attack. Meanwhile, the 2nd Mass must reassess their situation when an unexpected visitor appears.

The final standoff brings the Masons, the 2nd Mass, and their new allies into the bowels of an iconic American location, wrought with new and unpredictable obstacles. Despite great loss, they must persevere with hopes of once and for all reclaiming Earth and humanity.

On the outskirts of Charleston, the Mason clan and the remaining 2nd Mass suddenly find themselves under brutal attack by a new Espheni war machine - and a new deadly creation that is unlike anything they've previously encountered.

The Espheni reveal their new plan to Tom, and he is faced with an impossible decision. Elsewhere, Anne leads an exhausting search for her daughter Lexi, while Ben's concerns about Lexi's increasing powers uncovers a devastating secret she's been keeping.

Tom and the 2nd Mass hatch an elaborate plan to escape the confines of the Espheni Ghetto. Meanwhile back in Chinatown, Maggie confronts Lexi publicly about keeping a deadly secret. At the Espheni Youth Camp, Matt tries to talk Mira out of a dangerous escape plan.

After breaking out of the Espheni Ghetto, Tom and the 2nd Mass seek refuge in a Volm hideout, where tensions run high between the Volm and humans. In Chinatown, Anne is reunited with Lexi, and realises that the little girl she saw six months ago is now a grown woman.

After freeing Matt from the youth camp, Tom encounters two strangers in the woods, who attack his family before embarking with him on a violent journey. Hal faces almost insurmountable odds as he tries to lead the remaining Volm and 2nd Mass to a place of safety.

After months apart, Tom finally reunites with his family and the 2nd Mass but the joyous reunion is cut short as Lexi undergoes a health crisis tied to her hybrid DNA. The crisis pits family members against one another while Anne goes to great lengths to save her.

Lexi emerges more powerful and ruthless than ever. Tom and the 2nd Mass must work together with the Volm to hold off the invading Espheni forces in what becomes the bloodiest battle of the series.

The 2nd Mass picks up the pieces after an alien attack leaves Maggie fighting for her life... and Hal fighting for Maggie. Tom and Dingaan Botha are cut off from the rest of the group, buried under tons of rubble, where they must rely on an Enemy Ship to rescue them.

Attempting to dig out a shot-down Beamer, Tom and a small team follow the Volm to a supply cache in search of equipment to expedite the process. Back at camp, Ben teaches Maggie to hone her new skills, while Pope and Sara have a fight from which they may never recover.

Tom and the remnants of the 2nd Mass learn to pilot a Beamer as part of their plan to destroy the Espheni Power Core, and the group draws straws to see who will embark on the dangerous mission.

Tom's mission to destroy the Espheni Power Core is complicated by Lexi's return. Lexi has to take extreme measures to save her father's life - and her own - after a Beamer malfunction. Meanwhile, the 2nd Mass fears an impending Espheni strike by the scorched Overlord.

With the weight of humanity's survival on Tom and Lexi's shoulders, they must defeat Tom's mortal enemy and destroy the Espheni Power Core. Meanwhile, an Espheni bomb is dropped onto Chinatown - immobilising the 2nd Mass and preparing them for Human Skitterizaton.