Who is Gherman Klimenko from The Tears of Autumn and what is their importance?

Gherman Klimenko is a KGB agent whose cover since 1955 has been correspondent for the Soviet news agency TASS, Klimenko urgently contacts Paul Christopher in Rome to meet at St. Peter's, where he announces he is tired and wants to defect. Klimenko is short, bald, perpetually cold, and pathologically nervous. In return for Paul's help in reaching safety in the U.S.—insisting that Paul's cover as a writer has also long been blown—Klimenko identifies Frankie Pigeon as a sleeper KGB agent in the U.S. awaiting assignment since 1956. Klimenko has no direct proof, but everything points to Pigeon hiring Jack Ruby to kill Presidential assassin Lee Harvey Oswald.