Star Wars Twins, Separated at Birth : REDEYE<i> by Richard Aellen (Donald I. Fine: $18.95; 374 pp.) </i>

In his thriller, “Redeye,� Richard Aellen employs a familiar motif of low comedy and high drama--the confusion and chaos, whether intended or not, caused by the activities of identical twins. And in doing so, Aellen raises once again the intriguing questions surrounding such siblings, who, in fiction, often serve to personify good and evil.

Aellen’s twins fit neatly into this well-worn mold. There is the good twin--Paul Stafford, the star investigative reporter for the Washington Herald. The evil twin is Kurt Alexander, a professional assassin for the Staatsicherheitsdienst , East Germany’s equivalent of the KGB.

They are the protagonists in this uneven work that reflects the latest turn in U.S.-Soviet relations and the dramatic changes taking place in the Soviet Union under Mikhail S. Gorbachev. The plot appears to have been inspired by former President Reagan’s controversial conditional offer in 1983 to further world peace by providing Moscow with the secrets of “Star Wars� if the missile defense system is shown to be workable.

Aellen’s Soviet general secretary--who is never named--is preparing to leave for Washington to sign a treaty under which the United States and the Soviet Union will share secrets of their respective versions of “Star Wars.�

Soviet conservatives are opposed to the Kremlin reforms in general and to the treaty in particular. The far more sophisticated Soviet program, known as the Nevsky Project, has reached the operational stage, while its U.S. counterpart is still in the laboratories. So why, the conservatives ask, should Moscow exchange something proven workable for something that may never work? One of them, former KGB chief, Gen. Alexander Ikhnovsky, enlists Kurt to make certain that the treaty is not signed by doing away with the Soviet leader in such a way that Americans will be blamed.

To do that, Kurt is assigned to steal an obsolescent, but still effective, U.S. Redeye missile from a New Jersey warehouse to shoot down the general secretary’s plane as it is about to touch down in Washington for the signing ceremony.

The conservatives’ scheme begins to unravel because of good twin Paul’s nightmares. In them, he dreams, in grisly detail, of killing various individuals. Upon awakening, Paul sets down the nightmares on paper, along with the names of his dream victims, and sends them to a magazine as works of fiction.

The CIA finds nothing make-believe about them, for the stories are detailed accounts of actual murders of CIA agents or CIA “assets.� They believe Paul is the killer or at least an accomplice of the killer, who turns out to be Kurt. With great difficulty, Paul manages to convince CIA operatives of his innocence. He is helped by an attractive CIA “personnel specialist� who, fascinated by the special ties linking identical twins, provides the scientific jargon for Paul’s clairvoyance that enables him to “see� what Kurt is, or has been, up to.

Paul is placed under hypnosis to track the cause of his dreams. He mumbles the name of a depraved German “aunt�-- Tante Inge--that leads to the discovery that he has a twin brother. Each Berlin-born twin believed the other had been killed in the devastation and post-war deprivation of the German capital. Their war-widowed mother mistakeningly thought Kurt had met a gruesome death through the terrible Tante.

Paul and his mother, who is remarried to an American soldier, go to the United States where the good twin, blessed by the abundance and advantages of an American upbringing, grows into a sensitive, caring adult. Kurt, in the clutches of Tante Inge, remains in Berlin where he becomes a horribly abused sexual toy for Inge’s male and female patrons. He grows into a brutal killer whose only loyalty is to his mentor, Gen. Ikhnovsky, who had launched him on his career as a state assassin. Ikhnovsky’s given name became Kurt’s surname.

Kurt’s only flashes of humanity occur when, driven by curiosity, he enters into Paul’s world. But they are not enough to deter him from his mission. He laments the turn of fate that left him with Tante Inge, while his brother went off to the good life in America. Kurt even imagines he could have been the husband of the beautiful, dark-haired Joanna, whose marriage to Paul is disintegrating as a result of the accidental drowning of their only child. And he is eager to take Paul’s place in Joanna’s bed.

It is Kurt’s unprofessional and uncharacteristic detour into Paul’s life that leads to the final confrontation.

As a thriller, the book is off to a slow and halting start with too much emphasis devoted to Paul’s marital problems. The space could have been put to better use by building suspense in several episodes in the middle section. It is only in the final pages that the suspense reaches satisfying intensity.

Then, too, there is the business of Paul’s nightmares. His insights through “telepathic communication� give Paul a great--and in a way, unfair--advantage over his evil brother. Kurt possesses no such supernatural talents.

Also, the use of clairvoyance is a cut-rate way of advancing the action. When Paul reaches a dead end in his frantic efforts to thwart his brother, a dream leads him out of it.

Still, there are some nice twists to the plot. “Redeye� is a pleasant enough entertainment for both thriller buffs and those who are into dreams and other mysteries of parapsychology.