The killing rampage continues in the June 20 episode of "Harper's Island". After Madison is found and two fall as victims in the latest episode, the body number rises up to 15 but it will increase further. Through the preview, it is seen that Jimmy's life is supposedly taken due to a blast at the dock.
Also, Abby finds out that all the clues point out to one suspect, her own father. In the previous episode, Shane revealed to everybody that Abby is possibly the child of John Wakefield after Abby herself found the diary of the serial killer. A part of the journal which was saved from being burnt is read "Sarah had my child." Sarah is Abby's murdered mom.
The remaining people on the island also found a map which reveals a tunnel system under Candlewick. The episode is called "Snap" which may as well mean the next victim will die out of fracture.