THE FIVE: Our Very First Case, Part I Mystery Cache

In rural Pennsylvania in the 1950's, a group of boys formed a club. They were good kids, and loved solving mysteries--a lot more than doing their schoolwork! Since there were exactly five boys in the group, they naturally named the club, "The 5."
I had the good fortune to be one of the five; it was the happiest time of my life.

The captain of the club was named Russell Edmonson, but we all just called him "The Professor." His parents were both teachers at the local college, and we all expected the Professor to follow in their footsteps. Some of the school kids thought Russell was a bit stuck-up, but he was just more reserved. He made a great captain of our club.

Well, the first thing we had to do was find some place to use as our headquarters, or "HQ." When we looked around for a HQ, we found an abandoned "haunted" house on the edge of town. It was really scary looking--perfect for our HQ! Of course, we helped spread the rumor that the house was haunted, so that no one would discover the true use of the building. Here's a photo of our HQ:


Shortly after the 5 found their HQ, we got our very first case. There had been a robbery in town, and the home of Mr. and Mrs. Jennings was burgled of many of their possessions. Even their clothes were stolen!

The police made little headway in solving the crime, and the Jennings grew impatient. One day, they received a strange letter in the mail. The town police thought it was a joke, but the Jennings weren't so sure. So, they called the 5 to help.

The letter was just one page, with these funny words:

YIPWOOFWOOF YIPWOOFYIP WOOFWOOFWOOF WOOFYIP WOOFWOOFYIP YIPYIPYIP YIPYIP WOOFWOOFYIPYIP YIP YIPWOOFYIP YIP WOOF YIPWOOFYIP YIPYIP YIP YIPYIPYIPWOOF YIP WOOFYIPWOOFWOOF WOOFWOOFWOOF YIPYIPWOOF YIPWOOFYIP WOOFYIPYIPYIP WOOFWOOFWOOF WOOFWOOFWOOF WOOF YIPWOOF WOOF WOOFYIP WOOF YIPYIPYIPYIP YIPYIP YIPWOOFYIP WOOF WOOFYIPWOOFWOOF YIP YIPYIP WOOFWOOFYIP YIPYIPYIPYIP WOOF WOOFYIPYIP YIP WOOFWOOFYIP WOOF YIPYIPYIPYIP YIPYIP YIPWOOFYIP WOOF WOOFYIPWOOFWOOF YIPWOOFWOOFYIP WOOFWOOFWOOF YIPYIP WOOFYIP WOOF YIPYIPWOOFYIP WOOFWOOFWOOF YIPYIPWOOF YIPWOOFYIP WOOF YIPYIPYIPYIP YIPWOOFYIP YIP YIP YIPYIPWOOFYIP YIPYIP YIPYIPYIPWOOF YIP YIPWOOFWOOF WOOFWOOFWOOF WOOFYIP YIP YIPYIPYIPYIP YIPYIPWOOF WOOFYIP WOOFYIPYIP YIPWOOFYIP YIP WOOFYIPYIP WOOF YIPWOOFWOOF YIP WOOFYIP WOOF WOOFYIPWOOFWOOF WOOFWOOFWOOF WOOFYIP YIP WOOFYIPYIP YIP WOOFWOOFYIP YIPYIPWOOFYIP WOOFWOOFWOOF YIPWOOFYIP WOOF WOOFYIPWOOFWOOF WOOFYIP YIPYIP WOOFYIP YIP YIPWOOFWOOFYIP WOOFWOOFWOOF YIPYIP WOOFYIP WOOF WOOF YIPYIPYIPYIP YIPWOOFYIP YIP YIP WOOF YIPWOOFWOOF WOOFWOOFWOOF WOOFWOOFWOOF WOOFYIP YIP

After looking at the letter, the Professor started laughing. "Don't worry, Mrs. Jennings. I think we can get some of your items back."

What did the letter mean?