A scientist suffers a blood clot in the brain after an attempted assassination, and several men and a woman are miniaturized and injected into the scientist's bloodstream to remove the clot from the inside.
I first became familiar with this story through the novelization of the movie by Isaac Asimov. The movie itself never quite reaches the pitch of suspense to which it aspires, but this is a minor quibble; what it has going for it is a real sense of wonder. The scenes that take place inside the body are breathtaking and memorable, and very much of their time, as they fit in quite well with the psychedelic looks of the era; in particular, I like seeing the blue blood cells turn red inside the capillaries. It also seems to take place in fairly close to real time; once the crew is reduced in size, they have sixty minutes to complete their mission, which comes fairly close to matching the amount of running time left in the movie. The villain is almost a little too obvious, what with the casting, the constant harking by a certain character to abort the mission, and the fact that one character is obviously an atheist. Raquel Welch fans may be disappointed that she remains fully clothed the entire movie, though her skin-tight outfit aboard the sub may leave them somewhat satisfied. Amazingly enough, this is one movie that always seems to me to be shorter than its running time, which is indeed a good thing. Though not a perfect movie, it is extraordinarily efficient (they don't belabor the plot points) and quite satisfying.