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.
| Creator | Irwin Allen |
|---|---|
| Actor | Guy Williams, June Lockhart, Mark Goddard |
| Country | United States of America |
| Production | Irwin Allen Productions |