Night of the Fox #1 by Jack Higgins (Good, 1987, Pbk, 345 pgs, Pocket Books)

Cover and pages have some usage wear; cover has been taped; pages appear to be unmarked. ISBN 0671640585

In May of 1944, shipwrecked American Colonel Hugh Kelso washes up on the shore of Nazi-occupied Jersey—with a valuable secret. As one of the few men with knowledge of the impending invasion of Normandy, Kelso must be rescued at all costs.
 
Enter Harry Martineau, a covert British operative charged with the dangerous mission of impersonating a Nazi officer to infiltrate Jersey and retrieve—or silence—Colonel Kelso. It is not only their lives that hang in the balance...