Donald Duck is doing some camouflage painting on a cannon with yellow, green, and red stripes and black dots (the colors of the Flag of Lithuania with bullet holes in it). Sergeant Pete sees it and scolds Donald, claiming that anyone could recognize it. Peter demands Donald to re-paint the gun to make it "hard to see". Obliging to the sergeant's orders, Donald walks off to the "Experimental Laboratory: Camouflage Corps" disregarding the 'keep out' sign ("It didn't say 'positively' ", says Donald) and walks in. He finds some "invisible paint", which he tests with his finger and uses to paint the cannon.
When Pete arrives, he is shocked to see that the cannon is gone, believing it to be stolen. But it is not stolen as the sergeant finds out the hard way by bonking his head in the underside of the cannon and discovering Donald inside. Angered that Donald painted the cannon too invisible to look, Pete blows hard into one end of the barrel, sending Donald into the bucket of invisible paint. When Donald runs away from Pete, the latter finds out Donald has become invisible seeing Donald's footprints on the ground. Donald swims across a lake and the invisible paint doesn't come off.
Pete continues to chase Donald through a field of flowers, searching through the flowers, until he accidentally throws the flowers on Donald revealing his outline. Pete spots Donald and tries to catch him but Donald gets away again. The flowers give Pete an idea to find Donald. When the General drives up, Pete's antics, including jumping around a tree while singing "Here We Go Round The Mulberry Bush" and throwing flowers, convinces the General that he is acting odd, especially after Pete asks the General "did you see a little guy that you can't see?" and the invisible Donald puts a cactus down Pete's pants, making Pete scream in pain and jump around like a madman and the General wonders what is up with Pete.
Donald is running around a kitchen and then sees some pies in the window and Donald takes a pie and eats it. Pete then notices this and Donald throws the pie in Pete's face. Donald is skipping a rope, angering Pete, so he chases Donald around a tank. Donald then trips Pete, sending him literally under the grass, under some soldiers, and out again into the arsenal facility, where he gets hold of several grenades and begins blowing things up to stop Donald, literally on the warpath, starting with a pine tree that literally flies into the air and floats down. The General seeing this gets scared when Pete runs towards him and the frightened General hides behind a nearby power pole. The General tries to reassure Pete and stop his rampage, but Donald stands behind the General, who panickedly tries to tell Pete to calm himself, and when Donald pokes Pete in the rear with the General's sword, the startled sergeant jumps into the air and onto the General releasing all of the grenades that land on Pete and the General, injuring them in the explosion.
Later, Pete is locked up in a padded cell, wearing a straitjacket and chains, as he is declared insane by the army for his actions. He pleads to Donald (who is on guard duty and no longer invisible) to tell the General of his sanity, but Donald refuses, asking Pete "Do you think I'M crazy?" and whistles "The Army's Not the Army Anymore".