In this model there is one leader turtle and a group of follower turtles. The leader moves along a path according to a preselected formula (such as y = x^2). The followers move toward the leader with each step. The followers update their pursuit path each time the leader moves.
For detailed instructions on using the program, take a look at the info window from the Pursuit model.
Click on one of the pictures to see a quicktime movie of the model: