Out on his boat one day, a man gets dusted by atomic particles and starts—well, yes—shrinking. To infinitesimal size. Eventually he’s fighting for his life against the family cat and a passing spider. Most ’50s Sci-Fi movies were about common creatures attaining enormous proportions thanks to atomic misadventures, but this radical variation on that theme was (especially if you are a kid, eager to grow up, not down) scarier and more profound than the competitors. It is long past time for a cult to form around its director, Jack Arnold, an efficient maker of B Pictures (mainly Sci-Fi and westerns) whose imagination was always A plus.