Land of the Giants

Supposedly alien planet: the Giants have human Earth-type names.

Why can't the Earthlings contact Andre again? Granted, he's lousy at keeping secrets, but it seems silly to dismiss such a valuable ally out of hand, particularly given Kobick's final attitude toward Berger.

Andre isn't much of a conspirator: he leaves meetings with the Earthlings in his appointment book and detailed Earth schematics laying around his office.

Alternately, if the radiation effects are simply hallucinations, why is the invisibility so inconsistent? Berger wasn't exposed to radiation, so why is he hallucinating little people turning invisible? How does everyone have the same hallucinations (i.e., Dan, Steve, and Mark all see the cars and people vanish at the same moment)? And why do they have coordinated hallucinations (i.e., Mark hallucinating Steve vanishing, and Steve hallucinating that he's disappeared into some limbo at the same time?). Why does Berger hallucinate the disappearance of Spindrift, but not other surrounding inanimate objects?

So what the heck is going on with the radiation? If it's actually physically turning people invisible, why does it work inconsistently? It makes the Spindrift and the campsite turn invisible, but not the surrounding rocks and brush. It also works on Berger, who doesn't seem to have been exposed. How does it make the Earthlings "see" other things as invisible (i.e., the cars and people)? And how does it make just some inanimate objects disappear (i.e., cars)?

Once again, Betty's absence is pretty noticeable. Note that Fitzhugh is referred to as "the last one" and being "alone".