I Dare You

An invented hex now makes it impossible for Hermione Granger not to do as Draco Malfoy wants as long as it's phrased as "I dare you to...". Draco decides to make Hermione engage in a series of dares while he watches - which, over time, turns Draco on immensely (and unexpectedly). It also turns Hermione on, too . Eventually, they begin to both like it.