This week’s Puzzle Corner activity is a magic trick with a mathematical, as well as a slight-of-hand, component. I first came across this trick in one of Martin Gardner’s many books on recreational mathematics. I liked it so much that I have been stumping students, friends, and family members with it ever since. In order to make this trick work, you will need to practice it by yourself until the moves (illustrated at bottom) become automatic, before trying it out on someone else. Its success, like the success of many magic tricks, depends on diverting the audience’s in this case, your students’ attention. You can’t do this if you are uncertain of all the moves and take too much time making them. We’ll start by looking at how the trick is performed and then look at the mathematics involved.