Right after Mark has been teased by girls on the school boat, his cousin Virginia comes to stay with the Wedloes for the weekend. Mark tries to entertain her but she is reluctant to do anything. Mark and Virginia find an old sea mine in the channel while fishing and she won't help him move it so he goes to his father for help. Virginia talks to Ellen about being afraid, and Virginia decides to face her fears by taking Ben and some rope to move the mine. When Tom hears of this, he, Mark and Boomhauer race to stop her. They get her and Ben to safety just as the mine explodes.