By: Margaret Warner

SANA'A, Yemen | The stars are brilliant against the inky sky as we get off the plane late at night in Yemen. "Welcome to Sana'a," says our local fixer, a former journalist turned literature teacher, with a wide smile. The greeting from the airport authorities is less welcoming, as they pull us aside for a prolonged vetting of our equipment. But finally we're done and -- as the last private passengers to leave the terminal -- we're out in the crisp mountain air.

We speed through the city outskirts, far from the glories of Old Sana'a that my Moscow-based cameraman Denis Levkovich had photographed earlier in the day. But even in the light industrial area near the airport, many of the masonry buildings are festooned with intricate painted patterns that Yemeni architecture is famous for.

It's not hard to imagine that 2,000 years ago, this remote land of Yemen was known as Felix Arabia -- or "Happy Arabia." It was famed for the wealth it generated from the spice trade, and envied for the abundant rainfall that made it the lushest place on the arid Arabian subcontinent. It was home to the Queen of Sheba, and the place from where the three Magi set off to bring frankincense and myrrh to the Christ child. Seven centuries later, as Islam took root, Sana'a flourished as a center of Islamic architecture and culture.

Now, it's a benighted country - and a clear and present threat on the U.S. horizon. Statistically the poorest country in the Arab world, Yemen is fast running out of its modern-day export, oil, and the liquid of life, water. And ominously for us, it has emerged as the most dangerous new hotspot in America's struggle against the global jihadist terror network. Yemen is now home to the most potent of all the al-Qaida affiliates beyond the al-Qaida syndicate's headquarters in the tribal lands of Afghanistan and Pakistan.

It was here that the Nigerian student Umar Farouk Abdulmuttalab was recruited and trained - and equipped with a potent explosive as to come within a whisker of blowing up an entire plane of Northwest Airlines passengers approaching Detroit on Christmas Day. Perhaps it shouldn't have come as a surprise. After all, it was off Yemen's major coastal city of Aden that al-Qaida showed its teeth one year before 9/11, when it killed 17 American sailors with a suicide bomb attack on the USS Cole. But Americans tended to dismiss that as a lucky strike by a ragtag group of radicals. So when the would-be Christmas Day bomber's roots came to light, the reaction of most Americans was: Yemen? Why Yemen?

Our NewsHour team - myself, producer John Zito and my intrepid longtime cameraman-editor, Denis, have come to Yemen to try to answer those questions. Why, of all the countries on the face of the planet, is this isolated nation the one that threatens to become - in the words of Sen. Joseph Lieberman - "tomorrow's war" on the heels of Iraq and Afghanistan? And can the Yemeni and U.S. government do enough now to avert that catastrophe - without using American troops?

Check back in with The Rundown over the next week for more of my reporter's notebooks and blogs, audio or video shorts, photos and tweets. And tune in to the NewsHour March 22 to 26 for our entire week of reports from Yemen. We'll do everything we can to bring this mysterious place to life. For now - as midnight approaches in Sana'a - I'll content myself with gazing at the stars and anticipating what lies ahead.