This cadre is not the harnessed kids, who now live with the aliens. Nor are they those freed from the harnesses, such as Ben. He apparently still has positive feelings for the aliens, but so far he's likely done nothing on their behalf.
No, the fifth column - at least at this point - consists of just one guy, a military man from another unit, who talks our people into sending the children along with him for safety from an impending alien attack. Tom's not happy about it, but Ben talks him into it (does this mean that Ben is working with the aliens? maybe) and Tom then in turn sways the others, many of whom are understandably loath to let their children out of their sight or at least site. (That would have been my position as a parent, for sure.)
The one bright note in this is Tom's oldest son Hal has gone along with the kids, presumably because he is concerned about Ben. And Ben could turn out to be thoroughly loyal to his human family and species, despite the hints that he may not be.
So the fifth columnist will have his work cut out for him, as he delivers a human girl to a harnessed girl (who can speak, which make her more dangerous), and turns his attention to the children of our heroes and heroines, who don't yet know that their kids are a just a beat away from being turned over to the aliens ....
See also Falling Skies 1.1-2 ... Falling Skies 1.3 meets Puppet Masters ... Falling Skies 1.4: Drizzle ... Falling Skies 1.5: Ben
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The Plot to Save Socrates
"a Da Vinci-esque thriller" - New York Daily News
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