Viewers will feel the cold from the tomb that is Vietnam as ABC's "20/20" opens the stone door one more time tonight at 10 on Channel 7, but inside, they'll find only more disturbing questions.

Are there American servicemen still alive in Southeast Asia whom the rest of us, including President Reagan, have abandoned as we try to put that ugly war out of our minds?

Is the Pentagon victimizing bereaved families by sending home miscellaneous scraps of bone and incorrectly calling them the remains of a missing serviceman?

Tom Jarriel in his report comes much closer to answering the second question in the affirmative than the first. We do not come away from "20/20's" hour-long special, "MIAs: The Story That Will Not Die," with any new evidence that American prisoners still remain in Southeast Asia.

But we do see and hear impressive testimony during the unsettling hour that the Defense Department causes families fresh pain by the slipshod way it identifies remains.

"There is no professional quality to the work here," charges Dr. Michael Charney, director of the Center of Human Identification at Colorado State University, in appraising the Army's identification of a few scraps of bone as the remains of Marine Maj. Hugh Fanning. "This is outrageous."

We feel the Vietnam gorge rise again as Fanning's wife or widow -- we cannot tell which -- looks straight into the camera and with dry eyes tells what it's like to believe you have buried the remains of your husband after 17 years and then to be assailed by doubts that the man you buried was really he.

"I asked the casualty assistance officer much later if there was a hole in the skull . . . When he called me back he said, 'No there was no hole in the skull.' He failed to mention there was no skull at all . . .

"When people said, 'Kathryn, how do you know that you actually buried your husband?' I answered, 'Well, because the dental records matched the teeth.' It was totally by accident that I found there were not teeth, there was no skull. I exhumed the grave. I asked two board-certified anthropologists to examine the material. Both of them stated that these remains could not be identified as Major Hugh Fanning or any other particular individual."

The Army laboratory is repeatedly assailed during the program for such practices. But one brief scene of men sifting dirt at a plane crash site shows what the Army and other military services are up against as they try to end the anguish of MIA families.

The services, the program documents, do not have the resources to do the job right. Yet, like everything else about Vietnam, it is questionable whether any amount of money and specialists would answer the questions and end the anguish.

"MIAs" is not a "feel good" program. But it is comprehensive and balanced, not sensationalized. It forces us to look at the aftermath of a war everybody, including the nation's military, is trying hard to forget. And that has its uses, no matter how it feels.