The Fatal Impulse is an early, often maligned non-horror entry in the Thriller anthology series, and having seen it twice I found it effective for what it is,--a race against time to discover a bomb planted by a madman--which, while neither brilliantly written or plotted satisfies in its incidentals, such as the acting, notably by leading man Robert Lansing; the deliberate pace, urgent but not rushed, courtesy of director Gerald Mayer; and above all the mood, which conveys a a certain aspect of its time (1960) with spot on accuracy.
This Cold War was a literally hot button issue back then, as was the atom bomb. A bomb figures in the story (the Russians don't, as this is a local problem, a domestic issue). Still, madmen are madmen, and there's plenty of tension in the story. Lansing was the right man to play the lead, as there was always a near gloomy, no-nonsense quality to him. Moreover, there seems to be a dark cloud that hangs over the episode that comes from outside the story itself, which lends it an air of spooky nostalgia (for those of us who remember the era in which it was made).
Those were, for America, sweet days, and yet it wasn't all backyard cookouts and hula hoops, with Prince Charming JFK right around the corner. There was darkness, too (does it ever go away completely?), and The Fatal Impulse captures this aspect of its era to near perfection. The contemporaneous Twilight Zone was another TV series of the period that "didn't mince words" as to what was really going on just beneath the surface in the America of that time.
If I seem to rate this basically journeyman episode a bit higher than, on purely aesthetic grounds, I should, it's because of its channeling of a certain darkness in America that was not unlike the ticking time bomb at the center of the story, and tragically for us could perhaps not have been defused, whether or not there had been a presidential assassination or a war in Southeast Asia.