This film has a top-notch cast: Sam Waterston, Kathleen Quinlan, Jeff DeMunn and Yaphet Kotto and Richard Dysart. ........the action starts soon after the film starts and the suspense is sustained throughout the film, enhanced by a superior music score. Although the script is weak, the high action level and good performers sustain the entertainment until the end.
I like "Warning Sign" a lot as well. Besides the excellent cast, polished cinematography, and a pulse-pounding score, I thought the film offered some very pointed and provocative criticism concerning government arrogance and incompetence alike (the government creates the problem and proves to be totally all-thumbs when it comes to properly rectifying it). Moreover, the fact that the main protagonists were smart and capable adults rather than the standard array of dumb immature kids was a nice and refreshing departure from your usual 80's teen-oriented horror fare. I consider "Warning Sign" to be a very underrated medical sci-fi/horror sleeper: intelligent, absorbing and above all quite suspenseful.