Donald, who is tantalized by countless mosquitoes, asks Gyro Gearloose for help. And indeed, the ingenious inventor has a high-tec mosquito repellent for the bedevilled duck. Accidentally, however, Donald uses an invisibility spray Gyro developed for the army and becomes invisible. Several incidents and mosquito bites later Donald finally uses the right agent. The bloodsuckers disappear, only to make place for hundreds of butterflies who are magically attracted.