By design a person discovered that they had 18 hours to live and were unable to tell anyone about it.
Friends found it hard to understand why the person showed little interest in heated political conversations, in local gossip, or all of the very important discussions and projects that they wanted to engage their friend in. So little seemed to matter to the person.
During the course of the 18 hours, our subject came upon another individual whose life was in imminent danger. Our protagonist risked all to save the individual in danger. By design most of us have 18 more hours to live.