Whiz Tanner and the Secret Tunnel — Fred Rexroad

It's October and the air is getting cooler. But, that's not the only thing causing a chill for the proprietors of the Tanner-Dent Detective Agency. Best friends, Whiz Tanner and Joey Dent, the sixth-grade founders of our favorite detective agency, are hired to help settle a bet. Chuck Boyles and Thorny Rose are deep in an argument, which catches the imagination of the entire school. Chuck claims he saw a time-traveling automobile (a DeLorean like the one from Back to the Future) in Farmer Zimmer's barn. Thorny doesn't believe it. Easy enough to check out, except the barn is in a bull pasture. Getting around the bulls, and snapping a picture, turns out to be the easiest thing they do all weekend. And, that's only the start. Their little excursion to find the facts leads them into the middle of a robbery beyond anything they've ever encountered. Agents M and K make use of the most sophisticated equipment as they track down and aid in the recovery of very valuable Top-Secret stuff.