Well, it took about six months, but I've finally completed my quest of watching all 171 episodes of MISSION: IMPOSSIBLE. One of the last that I saw is also one of the craziest, even by M:I standards. It's from the sixth season (I watched the show in production order, but I found a couple of unexpected holes that I had to fill later) and is called "The Visitors." For a series based on preposterous plots, this one may be stretching credulity.
Edward Granger (Steve Forrest, later the star of S.W.A.T.) is a media magnate who owns several newspapers and radio and television stations. He's also in bed with the Syndicate and uses his holdings to influence the voters of his state to elect crooked officials. With just 72 hours before the next election, the Impossible Missions Force has to reveal Granger's plot to the public and ensure that the voters have the correct information before they go to the polls.
Granger is also a believer in extraterrestrial life, so what does the IMF do? Why, convince him that they're from outer space, of course. First, electronics genius Barney (Greg Morris) releases a mutated bee into Granger's house by placing a box with a bee and a fan in it over the chimney and blowing the bee out through the fireplace. It stings Granger (was it trained?) and releases an undetectable venom into him that completely paralyzes him. He can see and think, but he can't move.
His doctors can't do anything for him, but, that night, he looks out the window and sees a bright light in the sky that he thinks might be a UFO. Jim Phelps (Peter Graves) and Casey (Lynda Day George) arrive disguised as physicians and "cure" Granger using "futuristic" technology. They tell Granger that they're part of an alien race that chose Granger to join them in space 25 years earlier, but since he has become corrupt, he's no longer worthy.
Casey fakes injury in a car chase/crash, and Phelps and Granger carry her to the aliens' headquarters (which was obviously shot in the metal shop on the Paramount studio lot), where they place her inside some sort of rejuvenation device. It "returns" her to life, and Phelps tells Granger that he could have had the gift of immortality if not for his evil ways. Granger repents, and makes a statewide radio broadcast, confessing to his guilt and revealing to the entire state the names of the political candidates in the Syndicate's pocket.
Phelps, Casey and Willy (Peter Lupus) surreptitiously (as usual) slip out of the building and drive off during Granger's speech. A Syndicate gunmen, who followed the group to "headquarters," shoots Granger for his treachery, and the final shot freezes on Granger's bloody hand desperately reaching for the button that "operates" the machine.
Written by Harold Livingston, who specialized in far-out concepts (he also wrote "Encore," in which the IMF "de-aged" mobster William Shatner 30 years and convinced him the last three decades of his life never happened), and directed by Reza S. Badiyi, who specialized in arresting visuals, "The Visitors" may be the craziest MISSION: IMPOSSIBLE of all, but it's certainly entertaining.