With Hermione acting as a distraction Harry was able to plan. They were unsure when exactly the death of Myrtle Mayors had happened, so Hermione took it upon herself to befriend the fourth year girl in an attempt to keep her from having to hide away in bathroom stalls. Despite this precaution, they knew that it would be best to finish what they came to do sooner rather than later. After the third petrification Harry put their plan into action.