I was a greatly disappointed in this new series. The story started out pretty good but then fell into the same old "series" story line of trying to track down people. Very similar to the Sci-Fi series "The 4400", which had a strong start but by the time the premiere was over, it ended up just like all the others, the same old hunt and run story line.
All this reminds me of the old Doris Day movie "The thrill of it all". The company she worked with to promote their products produced a weekly TV show. It appears that the show was lame and had almost the same story every week with the same actors, only in different clothing and time settings. One week it might be Germany back in WWII and then the next might be a western. The producers said no one would notice the same story, but in the movie, the children did. Well, it seems Hollywood has the same plan, they just have a large pool of stories to repeat.
The first thing in Threshold that blew any form of realism in the story was when they boarded and searched the navy ship after they believe aliens were involved. No biohazard suit, nothing but gas masks with skin exposed. Doubt they would be that stupid in real life.
Next thing is when they decided to blow up a ship, which could scatter any contaminates that might spread. In the real world I would image it would be all about containment.
This kind of thing carried on throughout the entire show. Even at the end when they were planning to release the people who appeared to be drawn by the sound. In the real world, they would have at least quarantined them for a while until they could figure out what was going on. Actually, they probably would have pushed a contamination story to the public and isolated everyone they could that had any contact.
Another point that bothered me, it appears that they never informed the president of the country at any time. Seems that would have happened prior to them making contact with any possible alien life forms.
While all this might be trivial, it just destroys my ability to be pulled into the story. Of course, as with the show "The 4400", I will not bother watching this any further. I sure wish Hollywood some day would get a creative brain and get back to producing decent entertainment.