A Coast Guard boat is hunting in a fog for a smuggler disguised as a fishing trawler. The fog rises for an instant, disclosing the smuggler's position, and then quickly descends. The smuggler immediately departs at full speed on a straight line course of unknown direction. Assuming that both boats maintain a constant speed, and that the Coast Guard boat is faster than the smuggler, this Demonstration shows the course the Coast Guard vessel should steer in order to catch the smuggler.