Higurashi When They Cry: Time Killing Arc, Vol 2

Following a lead on the kidnapping of the construction minister's grandson, Officers Ooishi and Akasaka spot a secluded outpost station that shows signs of recent traffic. A little poking around brings them face to face with the boy's abductors, and the criminals aren't going down without a fight. Once the boy is recovered, the dam project is put on hold, and it seems to be a happy ending for everyone. What could Rika's warning possibly have been about...?