It was, of course, possible that the land beyond the Wall had been secretly invaded and conquered by-aliens.

One day, the earth is secretly invaded by an army of flying saucers, commanded by a Darth-Vaderesque alien called Glaxon (Rodger Halston).

Fifth Columnists had secretly invaded a free country.

He had looked for them for E ordinary volunteer enthusiast five years - those non-humans who had secretly invaded his Earth -- looked for them, despite constant failure, almost alone, unsupported, tormented by his beloved wife's disbelief, looked for them and found them.

They must call users, explain that their computers have been secretly invaded and talk them through the extensive steps required to remove the problem.

The Tsar has secretly invaded the Frontier because he wanted a conflict.

Said recordings proved that Pakistan Army had secretly invaded Kashmir.

Kenneth Von Gunden's 1990 novel Starspawn takes the same basic premise into a Medieval setting: England in the time of the Third Crusade is secretly invaded by parasites from space who attach themselves to knights and gain control of castles, and whose plot is eventually foiled by a wise and dedicated monk.