Lost in Space S01 E19 Ghost in Space

"A space colony family struggles to survive when their ship is hopelessly thrown off course."

Dr. Smith holds a seance to contact his Uncle Thaddeus. Instead a spirit creature is contacted and creates havoc for the Robinsons. It is later discovered that the ""spirit creature"" is a physical creature, rendered invisible by the properties of the ""ionized gas"" in the bog from which it came.