Natalia and Alexander Levchenko, a mother and son living in Moscow, know the dark side of glasnost. When President Bush finishes toasting and praising Mikhail Gorbachev this week, he should take the Soviet president aside and tell him this: If Gorbachev is serious about his country's image, he must let the Levchenkos go.

Stanislav Levchenko is a former KGB major who defected in 1979 and is currently living at an undisclosed location in the United States. He left behind his wife, Natalia, and son Alexander, now 25. By mutual agreement, the Levchenkos were divorced after his defection. Mother and son have paid the price for Levchenko's defection, and he is determined to get them both out of the Soviet Union.

The United States has been kind to Stanislav Levchenko. In Moscow he has been sentenced to death. He would be bound, but not blindfolded, and shot in the back of the head in a Moscow prison courtyard. But as a free man in the United States, he has published four books. He lectures extensively, consults with the Justice Department on espionage cases and is a fellow at Boston University.

Gorbachev has not been as kind to Natalia and Alexander. Levchenko had to sever contact with them for several years because the KGB was harassing his family to find out where he was. He thought he could make life easier for them if he didn't call or write.

He was wrong. Natalia has been allowed to take only low-paying jobs. Alexander was not permitted to enter college.

Levchenko contacted his family again last fall, hoping that Gorbachev and glasnost boded well for them. It did not. Natalia had the same dead-end job and Alexander was a night watchman at a dormitory, living below the Soviet poverty line, which is very low to begin with.

While Levchenko was out of touch, his son had been arrested on trumped up charges of "commercial dealings" and spent a year in jail. There he was beaten so severely that he lost the use of his right arm and leg.

The Immigration and Naturalization Service, at Levchenko's urging, has promised immediate entry into the United States as soon as Natalia and Alexander get exit visas.

Natalia was fired from her job in November when she applied for the visa. Last month, mother and son were denied visas on the grounds that they had access to state secrets -- a bogus argument the Soviets also use to detain Jews.

A deputy chief of the department of visas and permits in Moscow told Natalia, "You and your son will never leave this country. You are hostages here and will remain so forever."

On May 14, another bully in that department demanded Natalia take back the emigration applications. When she refused, he told her no one could help her, including the members of Congress who have written to Gorbachev to plead her case.

Alexander's health has taken a turn for the worse. When we recently visited Levchenko, a friend of several years, he was severely depressed. He told us his son was talking about suicide, perhaps by setting himself on fire, the same method used recently by a Lithuanian who also wanted to get the attention of Gorbachev.