BASED ON the true story of a group of escaped East Germans who tunneled back under the Berlin wall to rescue some 30 friends and loved ones left behind in the early 1960s, "The Tunnel" is a rip-snorting adventure yarn starring Heino Ferch, a Teutonic Bruce Willis whose lumpy, blue-collar charisma is a perfect fit for the role of the dogged hero-with-a-shovel Harry Melchior. Although it doesn't require any deep thinking or heavy lifting (at least not on the part of the audience), it's good old-fashioned movie storytelling that steadily builds, over the course of nearly three hours, to a white-knuckle conclusion that satisfies on nearly every level.

I only wish that there had been a little more explanation of a couple of nagging questions I wasn't quite able to shake. As the group of tunnelers grows from Harry and a few friends at first -- engineer Matthis (Sebastian Koch), American Vic (Mehmet Kurtulus) and upper-crusty Fred (Felix Eitner) -- to a cadre of more than 10, including sexy female co-conspirator Fritzi (Nicolette Krebitz), it's never clear exactly how this massive undertaking is being paid for. Sure, there's a scene where the core group is interviewing potential collaborators, and one guy is asked how much money he has. For the most part, however, we're left to imagine where food, shelter and equipment for the diggers comes from.

Midway through the project, an NBC film crew gets wind of the tunnel and pays a lump sum to each of the diggers for permission to film them. Other than that, though, the project's not insignificant finances -- and surely the cavernous factory they rent across the street from the wall wasn't free -- remain a mystery.

My other quibble? The dirt. In 1963's "The Great Escape," another excellent tunnel flick, we were at least shown how the POWs disposed of all the displaced soil (distributed in the prison yard via the legs of their pants). In "The Tunnel," who knows where it all goes? Does it get piled up in some back room? Carried out in trucks? Beats me.

But as I say, these are quibbles.

What we do see is how Harry and his friends stoically cope with one setback after another: a concrete wall they hadn't planned on running into; a burst water pipe; a near-fatal cave-in; informants on the other side; the capture and temporary imprisonment of Vic while on a message run through Checkpoint Charlie; and an East German security officer (Uwe Kockisch) with the tenacity of a pit bull and just enough information to be always one step away from uncovering the whole operation.

Make no mistake. "The Tunnel" is not a documentary. There's a love triangle, an attempted suicide, close calls out the wazoo, and heroes and villains writ as large as in any Hollywood thriller.

Is there ever any doubt about the film's outcome? Not much. Still, it's so well told that you'll be biting your nails until the film's final few minutes.

THE TUNNEL (Not rated, 160 minutes) -- Contains obscenity, a sex scene and some violence. In German with subtitles. At Landmark's E Street Cinema.

Fritzi (Nicolette Krebitz) grieves for her boyfriend, trapped on the east side of the Berlin Wall.