Just trust us!
Threshold was the least interesting of the three 2005 TV first-contact series. Its pilot was intriguing, but after a few episodes, it seemed to have exhausted its meager deposit of ideas; all the essential questions about the aliens—intelligent or not, extraterrestrial or not, hostile or not, had all been answered, before there was even time to ask the questions. Threshold was canceled after only a half-season.
Threshold's aliens came from above, but were first spotted over water, by a US Navy vessel. An obviously extraterrestrial object appeared off its bow, and began emitting a signal which killed some of the crew, and began a genetic mutation of others, who survived. Some of them escaped to the mainland, and began trying to recreate the signal in a way that will cause millions of Americans to be changed into the clearly malevolent aliens. Not to worry, though, the government had it all under control, by enlisting the aid of Molly Caffrey (Carla Gugino) who designed Project Threshold for just such an emergency.
Threshold's directors operated under the myth that darkness = suspense, which good directors such as those of Invasion and Surface have happily outgrown. Having its team members work in dimly-lit, gray rooms, doesn't magically give the series a desperately-needed spark. Threshold settled nto a "freak of the week" format, where a la The X-Files, half the team dashes across the country to a new locale every week to investigate alien activity. Threshold further suffered from having nearly every episode directed and written by another person. Not exactly a recipe for continuity.
Furthermore, there is nothing of spiritual or philosophical interest here. Threshold lacks both Surface's drive for understanding and Invasion's depth of mystery. The aliens are simply wholly alien—They are them, we are us, and we need to protect us. If the Bush administration wanted to create a sci-fi series to promote the institutionalized anxiety known as "the war on terror," it would be a lot like Threshold.