The preeminent concern of the early 21st century -- terrorism -- now prompts a refined counterpoint to what's become an obsession with American TV dramas, and it puts most of them to shame. This BBC series, which aired in the U.S. on the A&E cable network, follows a cadre of elite agents from "Section B" of the U.K.'s MI-5 spy shop. Experts in counterterrorism, these funny, flawed people -- the spot-on ensemble cast is led by a charismatic Matthew Macfadyen -- juggle messed-up personal lives, in which they must lie to even the people they love, and a covert war on the streets of urban Britain. Tense, timely, and eloquent, the series takes on hot-button issues including abortion, race relations, political protest and revolution, and even governmental scandal. This is smart, sophisticated stuff, uncompromising in its unwillingness to see anything in black-and-white. Each of the six episodes contains 15 extra minutes of footage unseen on American television, as well as cast and crew commentaries and peeks behind the scenes, and the three-disc set sports one of the cleverest DVD-menu schemes I've ever seen.