The Twilight Zone - Season 1 Episode 2

Salesman Bill Lowery wakes up one morning and discovers, to his horror, that people around him are slowly degenerating their talk into gibberish that he cannot understand. His ability to communicate is needed more than ever when his son becomes sick. Lowery manages to get his son the treatment he needs and discovers he must relearn everything from scratch. On an idyllic outdoor picnic with her husband and their twins a nameless woman becomes confused and disoriented when events begin to repeat themselves. A space shuttle returns from a mission and NASA discovers that something unusual has been picked up. They discover that they have a shape-changing alien in their holding tank that poses a danger to all.