If the TV biz, like professional sports, gave out a "most improved" award, then The Invaders would be a prime candidate. Not that the first season of this ‘60s sci-fi/adventure series was bad, as it dutifully introduced the concept (aliens from a dying planet have come to Earth to lay the groundwork for a massive invasion) and the hero (Roy Thinnes as architect David Vincent, who sees the spacemen land and becomes obsessed with stopping them and alerting his fellow humans to the threat). But the second season, delivered here with 26 episodes on seven discs, hits the ground running, greatly amping up the tension and sense of imminent dread. For one thing, while Vincent is still the main man, many others now realize that there are aliens among them; just four episodes in ("Valley of the Shadow"), an entire town watches as an alien glows red and then disintegrates after being shot, and about a third of the way through the season we learn that Vincent is one of a small and valiant group of so-called "Believers" who have dedicated themselves to thwarting the bad, um, guys (who, although they lack blood, a pulse, and a heartbeat, look just like humans, save for their distended little fingers). And Vincent himself doesn’t just root out aliens anymore--he converses with them, negotiates with them, considers working with them, and even kisses a comely female (in "The Life Seekers"). As for the invaders, they still have a host of dastardly methods for wiping out Earthlings: disabling the military’s air defense system before their ginormous invasion flotilla arrives, upping the radiation in the atmosphere to lethal levels, assembling the world’s leaders in one spot under false pretenses in order to wipe them all out, and so on. But while their ray guns, spaceships, brainwashing devices, and various other technologies are way ahead of ours (the effects work is still primitive, but there are plenty of fistfights and chase sequences to make up for that), they are not infallible; and it’s their very lack of human emotions that may prove to be their undoing. But we’ll never know, because Episode 26, "Inquisition" (in which Vincent and his allies determine exactly when the alien invasion will occur), was the last one produced. As was the case with the first season boxed set, Thinnes’ episode intros and a new interview with the actor are the main bonus features.