Stargate SG-1/Recap/S2 E13 Spirits

SG-1 finds a planet inhabited by Native American Indians, protected by spirits who are actually advanced alien shapeshifters. The Pentagon learns that the phrase "what they don't know won't hurt them" is a really bad thing to say when the people you're trying to hoodwink are guarded by a very powerful alien species capable of, once again, walking through walls and turning invisible.