Somehow this runs out of standards stablished beforehand on The Time Tunnel Series, this turn our heroes were transported to 1547 on sixteen century somewhere at Grand Canyon, so it's supposed any specific major event in the history why they are there, previously in the Time Tunnel complex a spy called Nimon (Robert Duvall) planted a nuclear device that should explode in few hours later, after he escaped through the own Time Tunnel ends up at Grand Canyon, Gen. Kirk demands that Tony and Doug find out he nearby, soon they find him, when they catch Nimon he sudden disappears going into the future more precisely one million A. D. followed by the duo.
They are materialize in kind of strange civilization akin Bees colony, consisting in three level of people, the workers, the guardians and led by the sages, aside it was a supposed and futurist world, actually they weren't an advanced race, Nimon was there to developing a time travel system about to starting the early transport texts using human beings since that there aren't any animals available at its time, Tony and Doug intervene due it shall kill the woman used as guinea-pig, while this in Time Tunnel complex the whole security crew try find out the nuclear device without success, then they transport our friends bringing together Nimon the women Zee and the guard Vokar now in opposite range of time one million years B. C. among pre-historic monsters Tony and Doug have to get the information from the own Nimon where is the bomb in time to save the Time Tunnel Complex.
Aside a slight rambling the plot is quite tense due the nuclear device that wasn't locate by the security members and the time is running out faster as Irwin Allen wisely imposed, finest episode!!
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First watch: 1971 / Source: TV-DVD / How many: 5 / Rating: 7.5.