In Russia, KGB intrigue; One Small Clue, by Mara Kay. New York: Crown Publishers Inc. 121 pp. $8.95. (Ages 11 and up.)

John and Madge, twins, find out on their birthday that their mother was not American but Russian and that their father may still be alive in Odessa. On a sojourn to Russia, they hope they will be able to uncover the truth about their past and their present.

During their search they encounter, among others, the Bulanovs, two Russian children whose older brother is writing a book which speaks out against the Soviet system; Joe, an old Russian sailor they hope will reveal a clue as to their father's identity; and Victor, a thin, dark-haired boy who lives in the same building as the Bulanovs, and who spies on them.

But the twins seem to get nowhere in their search - except into trouble. Who is following them? Why do KBG men show up at the places they have visited, asking questions?

The characters are a bit stereotyped, but the author has made an attempt to explore some of the meanings, and surprises, of discovering one's roots.