Invasion — Murray Leinster

In Murray Leinster's "Invasion," the unthinkable has come to pass -- a spacecraft has touched ground on American soil with intentions that seem to be nefarious. A lone U.S. soldier is trapped within the vast force field surrounding the ship, and he quickly determines that all is not as it appears to be. Will this intrepid warrior be able to communicate what he knows and thwart the invasion?