The Mystery of the Night Raiders

When the girls go on vacation, their scientist neighbor, Mr. Gordon, agrees to take care of their dogs and goats.  When Mr. Gordon goes to feed the animals, one of the goats tells him that during the night there were mysterious noises and shadows where the dog treats are stored.  The big dogs scared them away, but who were the mysterious night raiders?  Though the girls have some interesting guesses, Mr. Gordon tells them it is best to use evidence to find the answer.