PBS walks softy and carries a big stick. When considering great contemporary television, it’s easy to dwell on the mature, polished programming of the big cable channels and forget all about PBS, even though its stations have been bringing excellent and diverse shows to us for decades. It shouldn’t be a surprise, however, since the big stick, the secret weapon they’ve been swinging for years, is none other than the BBC, a giant which is arguably the source of the greatest television in the world. PBS, and especially “Masterpiece,” has long been the conduit for the strongest shows from across the pond.

“Page Eight” is no exception, an effortless, elegant spy thriller in which not one shot is fired, not one car is blown up, and there are no countdown timers.

The centerpiece is Bill Nighy (“Underworld,” “Pirate Radio,” “Shaun of the Dead,” “Love Actually,” and about 100 other things since the 1970s), who is always a welcome sight, though rarely the main attraction. He plays Johnny Worricker, a long-time MI5 analyst who finds himself in possession of a document with dark implications for both the agency and the entire British government. While Nighy is capable of chewing up scenery with the best of them, he plays Worricker with perfect restraint. Like some kind of master hypnotist, he takes us slowly inside the old spy’s mind, heart and history using his voice alone.

Upping the ante is the masterful Sir Michael Gambon (who has been in everything from “The Cook, the Thief, His Wife & Her Lover” to “Harry Potter”) as Worricker’s  friend and boss Benedict Baron. When the two of them are onscreen together their interaction is so delightful one can’t help but smile, and just like that, the whole sneaky spy mess lightens up a bit. The BBC should consider a spin-off in which Nighy and Gambon just sit around and talk about stuff.

Conversely, Ralph Fiennes as the prime minister brings a menacing, iron gravity to the politician without ever uttering a single threat, and Saskia Reeves (“Inspector Lewis,” “Luther”) plays the Home Secretary with a gratifyingly unstable snarl.

Surrounded by such formidable talents, it’s not surprising that Rachel Weisz comes off a little light as Worricker’s neighbor who might, or might not, have her own agenda. It’s a weak point in the story, since her role as a possible romantic interest, though it might be necessary, is not very convincing.

How do you tell a gripping spy story without guns, bombs or sexy music? The same way performers have been enthralling audiences in amphitheaters for thousands of years—with a bunch of talking and their own formidable sorcery, acting. Stepping back from the typical American cinematic assault of quick cuts, flashing lights and loud noises and submersing oneself in the best the BBC has to offer is like remembering what it feels like to be human.

“Page Eight” may currently be streamed online at www.pbs.org.