Grey's Anatomy

The world is left in tatters after a sudden, unprovoked and unexplained invasion by aliens, leaving the planet's remaining human population to fight for survival against the occupiers. History professor Tom Mason has been named second-in-command for the 2nd Mass, but his real focus is on his three sons, one of whom has been captured by the aliens for an unknown purpose.

While scouting for supplies, Tom, Hal and their squad encounter a gang of marauders determined to get their hands on the 2nd Massachusetts' weapons. Leading the gang is an ex-con named John Pope, who decides to use his hostages as bargaining material.

During a rescue mission that could mean the survival of his family, Tom has a harrowing one-on-one encounter with an alien skitter. Harris, a doctor who has a history with Tom, arrives in camp and may have a way to save harnessed kids.

After reluctantly agreeing to bring Pope along on a mission to retrieve motorcycles, Tom and his men are attacked by something harder to fight than aliens. Anne and Dr. Harris make an important discovery.

Hal comes up with a risky and dangerous plan to infiltrate a skitter's lair and rescue Ben and other harnesses kids that are being held captive.

Another resistance militia leader, Clayton, arrives in camp warning of a coming alien assault, and with time running out, Tom and the camp must weigh his offer to take their children to a safe haven.

Hal begins to suspect the farm is not the idyllic safe haven Clayton said it was, and when Mike stumbles upon the horrifying truth, he and Hal find themselves up against an unforeseen enemy.

Weaver becomes increasingly unstable and causes trouble for Tom and Hal while out on a recon mission. Pope pieces together a formidable weapon, and Anne autopsies a skitter carcass, making an astonishing discovery.

Escalating tensions between Weaver and Tom threaten to tear the 2nd Mass apart on the eve of their important attack on the alien base structure.

Hal, Weaver, Pope and others embark on the 2nd Mass' most ambitious assault, while Tom must defend the civilian camp against a surprise alien attack, leading Tom to an encounter with an alien being which could change his life forever.