The rules for a weeper, a movie tear-jerker, could not be simpler. Touch us. Make us fumble around in the dark for a Kleenex. But earn those tears.

"Seven Pounds" is a weeper wrapped in a mystery centered on an enigma. But whatever pains cast and crew go to preserve its mystery, the movie's tears are righteous, as is its message.

Ben Thomas (Will Smith) is a serious, sad-faced stranger who walks into people's lives like some sort of angel. The first piece of the puzzle: Is he the Angel of Death or a guardian angel?

Ben's an IRS agent, so he has access to people's entire lives. He shows up, unannounced, and interviews folks — interrogates them actually. He's tactless, a little rude. They're in arrears on their taxes, upside down on their mortgages, in failing health or leading lives limited by circumstances beyond their control.

Who is he? What does he want? What is his mission?

"No questions," he fires back to one and all.

Emily (Rosario Dawson) is one who won't take that for an answer. She has congenital heart failure. She's deep in debt. And this callous fed seems to be stalking her, seeking to discover, as he does with a blind musician (Woody Harrelson), kids' hockey coach (Bill Smitrovich) or nursing home operator (Tim Kelleher), if she's a "good person."

Smith's "Pursuit of Happyness" director Gabriele Muccino, working from a script by TV writer Grant Nieporte, gives us enough glimpses to guess the big mistake that Ben is atoning for in meeting these people and studying their lives. And since the opening moments of the film are a 911 call, we know where this might go if love, joy or happiness don't intervene.

But forget the puzzle, the cryptic touches and the bracingly sad little music montages that Muccino packs in as filler. "Seven Pounds" sinks or swims on the Ben and Emily connection; Dawson ("Eagle Eye," "The 25th Hour"), rarely used on film in this way, simply will not let it sink. She lets the camera see what Ben sees in her eyes, the good humor and hope that mask the weariness of a deadly illness.

Harrelson and Barry Pepper (playing Ben's best friend) make the case that they each deserve more work than Hollywood offers. Smith usually plays such awards-bait roles with a sullenness that robs him of his movie-star qualities. Not this time.

It's not a masterpiece, but "Seven Pounds" is perfect in at least one way — its timing. An emotional movie at the most emotional time of the year, it works to keep its secrets. But more importantly, when the tears do come, it has earned them.