The Girl in the Window - Lindsey Hobson

When Izzy breaks a window in the creepy house next door, her summer plans suddenly go from playing baseball in the backyard to doing yard work for mysterious Mr. Johnson to pay for the damage. Just when she thinks it can't get any worse, she encounters a ghost girl with a cryptic message: HELP ME. As Izzy begins to unravel the mystery surrounding the girl's death, she discovers a whole new meaning to being friends... forever.