1861. Abraham Lincoln orders that the First Transcontinental Telegraph line, currently interrupted between Nevada and Nebraska, be completed. Two teams, one heading east from Carson City and the other west from Omaha, will meet up in Salt Lake City. Lucky Luke joins the eastbound team. But when a £100,000 reward is offered to the first team to arrive, there's suddenly more to fear than the natural obstacles of the journey: A saboteur seems to be at work!