Best of Enemies — Carolyn Keene

AMERICA'S HOTTEST TEEN DETECTIVES TEAM UP TO BRING AN AMERICAN SUPERSPY TO SAFETY
The Berlin Wall has come tumbling down, and a major American agent -- code-named the Swallow -- wants to come home. On a top-secret mission for the Network, THE HARDY BOYS head to Memphis, where a mystery man named Pritchitt has promised to turn the agent over for a price. But a ruthless German spymaster, known only as Klaus, has vowed to beat Frank and Joe to the punch -- and shoot the Swallow out of the sky.

Meanwhile...
NANCY DREW comes to the aid of Beau Davis, a guy with a bad case of the Memphis blues. Accused of stealing a guitar once belonging to Elvis, he is now a prime suspect in a more ominous matter -- the murder of Pritchitt! In a case as twisty and treacherous as a Mississippi River current, Frank and Joe and Nancy are headed for a stunning rendezvous and revelation...