‘Invasion,’ 10 p.m. ABC; E-Ring,’ 9 p.m. NBC

Tonight’s two new dramas owe much to what has come before.

The better of the two, “Invasion,” can be summed up in four words: aliens walk among us. It’s long been a mantra of science fiction, especially when national anxiety about the unknown runs high. It’s as old as “Invasion of the Body Snatchers” and as new as “The X-Files.”

“Invasion” starts right off with a hurricane approaching Florida (not the greatest of timing following Katrina, but essential to the series’ plot).

The hero of this piece, park ranger Russell Varon (Eddie Cibrian, “Third Watch”), joins his extended family to wait out the storm. Much tension ensues, as one family member wanders off, while another is late in returning.

During the storm, his physician ex-wife Mariel (Kari Matchett) disappears on her way home. This brings by her worried new husband, arrogant local sheriff Tom Underlay (William Fichtner, “The Longest Yard”). The two form an uneasy alliance and eventually find Mariel in a strange location.

Russell notices that Mariel is acting a bit off. In fact, as he looks around his little corner of the world, he sees more and more people behaving bizarrely.

Russell’s layabout brother-in-law Dave (Tyler Labine), a conspiracy buff, has been gathering evidence of odd goings-on, but because of his reputation, nobody is really listening, not even Russell.

This intriguing “Invasion” has “Lost” as a lead-in, and it will need all the help it can get, going up against the perennial “Law & Order” and “CSI: NY.” Maybe, just maybe, creator Shaun Cassidy will get the hit he deserves that eluded him on such earlier creative efforts as “Cover Me” and “American Gothic.”

Also debuting tonight, “E-Ring” is, as a concept, “The West Wing” goes to the Pentagon, taking viewers inside the Washington decision-making process. The series follows Major Jim “J.T.” Tisnewski (Benjamin Bratt, “Law & Order”), a Green Beret who is learning his way around the Defense Department headquarters.

J.T. reports to the eccentric Colonel McNulty (Dennis Hopper on cruise control), a character who’s just as likely to be listening to classic rock or selling timeshares or figuring out his football-pool slip as he is planning a high-tech mission.

“E-Ring” features much cutting between troops in the field and the planners in a Pentagon ready room. There’s plenty of action with a healthy dose of jingoism. Think of it as that longtime war horse “JAG” with more personality.

“E-Ring” is diverting enough. Still, with uber-producer Jerry Bruckheimer (“CSI,” “Without a Trace”) and Oscar-nominated director Taylor Hackford (“Ray”) behind the scenes and Bratt and Hopper on camera, this should be more. The sum doesn’t really equal the parts. Still, as one of four new shows in its time slot, it’s got a good chance of surviving.