This is exactly why I have such great admiration for Rod Serling! Just when you - albeit reluctantly - accepted that yet another episode will suffer from a predictable and overly sentimental climax, the script comes up with a simple but very effective and pleasant end-twist that catches you by surprise! Old-timer Sam Forstman is obsessed with keeping his clock, a family inheritance piece, ticking. He firmly believes that, when the clock stops ticking, his own heart will too. Sam's increasingly paranoid behavior causes stress and tension with his pregnant granddaughter and her husband, where he lives with. I don't want to spoil the (anti-)climax, but it so incredibly good! And the reason why it's so good is because it is genuine, reasonable, from the heart, and natural. In fact, you might even say the twist is anti-Twilight Zone.