Complex sentence: The scientists' plan is for Dr. Leighton as the Thetan creature, equipped with a energy weapon and spaceship, to land at the United Nations in an effort to create panic initially, that will be resolved as the world unites to fight the invader.
Split into simpler sentences: The scientists' plan is for Dr. Leighton as the Thetan creature, equipped with a energy weapon and spaceship, to land at the United Nations in an effort to create panic initially. This panic, in theory, will be resolved as the world unites to fight the invader.