The Seaview discovers the remains of an ancient civilization in which are scattered cylinders that appear to hold survivors in suspended animation. This is one of the better 'pure sci-fi' episodes of the first season and guest star Robert Duvall is excellent as Zar, the 'invader' from the deep past. Despite some minor plot issues (Zar's explanation for how he learns English seems inconsistent with his early proficiency and his final 'bargaining chip' is a bit convenient and contrived), the story is well told and interesting with a well-done pragmatic and 'realistic' (as these things go) resolution. Duvall's talent as an actor is on display in this outing (which is more than can be said for his portrayal of a chrome-hatted time-jumping nasty in the limp 'Time Tunnel' episode 'Chase Through Time '.