From Beyond 4K 1986

According to the theory of the scientist Pretorius, man, unknowingly, coexists with another invisible world surrounding us all the time. The key to penetrating this parallel world is our "third eye", an inactive organ in the frontal area.

When the resonator (the machine that Pretorius created to stimulate the "third eye") worked, the scientists managed to penetrate the empire of the "sixth sense" and cause confirmation from the outside: they saw creepy and disgusting creatures gliding around them in the air! But one of the monsters suddenly became enraged and bit Pretorius's head off.