I was surprised as I watched "Quantity: Unknown" as it managed something no other episode had done before....it was very badly written. Up until this episode, I was pleased with every show...but this one is just bad for many logical reasons.
When the story begins, a small plane crashes and the crew is gone...which means they were likely aliens. Among the things found after the crash was a small cylinder which was VERY weird, as it had no weight whatsoever. Not surprisingly, David learns about it and comes to investigate.
Now the set-up for this one was excellent....but what came next was just bad. David joins up with another guy who he assumes is an alien hunter like himself....though he really has no proof of this. And, what they do next makes no sense at all. To top it off...the ending make no sense either. After all, David was smart in all the other episodes...and here he is a complete idiot and very gullible.
A few of the logical errors would include the chase at the end of the show (David has a gun....yet runs from his pursuer who has none and is planning on killing him), the 'friend's' actions at the laboratory and much, much more. Did the producers decide to let their kids write this one?! A huge disappointment with so many logical errors I'm not even going to mention them here!