While at the hospital for Buffy's mother, Dawn picks up a stethescope for fun and listens to people's hearts.  When she gets to Riley's she hears it beating way too fast.  Riley is having a reaction to the Initiative "training" and his heart is being pushed to the limits.  Since this causes his to have greater than average stregth, he doesn't want to end it because he feels that Buffy won't want him anymore.  She convinces him to get it taken care of but not before Spike and Harmony kidnap the doctor so that he can remove the chip from his head.