IMAGINE, if you can, this scenario: An American professor, perhaps at a university like Harvard, speaks out against the Reagan administration. The issue might be Nicaragua, or ``star wars,'' or immigration policy.
The administration warns this erring professor, and his outspoken wife, to be silent. They fail to heed the government's injunction. The government carries out a series of increasingly harsh punitive actions.
The professor is stripped of his job, prevented from talking to the press, harassed in dozens of ways, and finally sentenced to exile in remote northern Maine.
There, he and his wife have their mail censored, their telephone calls regulated. Their contacts with their family are restricted. They are barred from talking with reporters, and reporters are prevented from visiting them. From time to time, they smuggle out messages to their friends.
They are under surveillance and threat of further government action. They are secretly filmed by the authorities.
A sizable security apparatus is devoted to keeping these two elderly critics in isolation and preventing them from voicing their dissent from certain aspects of official policy.
The government's inhumane action rouses a storm of criticism outside the country, but the government remains adamant.
The professor's wife wants to leave the country for medical attention. The authorities in Washington refuse. The professor goes on a hunger strike.
Eventually, while the professor is kept in Maine for insurance, the wife is permitted to travel to a country outside the United States, provided she promises not to talk with the foreign press about the treatment to which she and her husband have been subjected.
If a novelist submitted to a publisher such a plot for a book, it would be dismissed as bizarre and implausible.
Yet move the locale from the United States to the Soviet Union and fantasy becomes fact in the experience of Andrei Sakharov and his wife, Yelena Bonner.
Miss Bonner has returned home to the Soviet Union after six months in the West. Her parting words were words of anguish:
``I have not the slightest desire to return . . . anyone in a sound mental state would not want to return from freedom to prison. I am returning there only to be reunited with my husband.''
Two American congressmen accompanied her back to the Soviet Union. Western diplomats and newsmen were on hand to mark her arrival in Moscow. There was no overt harassment by the KGB. Miss Bonner was moved through Soviet customs without incident.
Indeed, at her Moscow apartment house, where she was allowed to stay briefly en route to Gorky, the stairwell had been repainted and new grass had been sewn outside.
We should be grateful for such civilities -- but not too grateful, for as one of the congressmen, Barney Frank of Massachusetts, said: ``We should not appear excessively grateful for small favors. What happened was that the Soviet authorities treated her like a human being.''
If the Soviets treated the Sakharovs, and more of their citizens, as human beings more often, it would do more for their image than almost any other policy change one can imagine them making.
Given their terrible losses in World War II, one can understand the rationale behind their preoccupation with military power.
And if the Soviet leaders insist on pursuing an economic system that has proved ineffective, well, that is their privilege.
But what is unforgivable to many outside the Soviet Union is the harsh treatment of human beings, and the imprisonment within Soviet borders of those who do not wish to be part of the system.
The Western campaign to ease the plight of the Sakharovs is no campaign to embarrass the Soviets. It is a genuine reaching out, an inherent concern for humanity unjustly treated, that the Soviet system seems incapable of comprehending.