The evil magicians called the Mesmers are still plotting to take over the world, and the Kennewicketts, recently recruited into the spy business by President Roosevelt, are at the center of the battle for world domination. Now the Amazing Automated Inn has been compromised: someone is smuggling secrets out of the lab and selling them to unscrupulous sorts in Italy. Worse, their friend Nikola Tesla's latest invention--a device that will provide a limitless and free source of electrical power for all--has been sabotaged.

Determined to stop the villains, the Kennewicketts and their staff of automatons travel to Italy in the Daedalus, a lighter-than-air ship. At first, the trip goes as planned, but then another airship manned by murderous sky pirates chases the family over the Atlantic. Luckily, Wally's latest invention, a man-lifting kite, allows them to reach land safely, where they are rescued by the Arachne, a giant steam-powered mechanical spider with a luxury yacht interior that can move at over seventy miles-per-hour! An exciting adventure over the Alps aboard Arachne with the pirates in pursuit ends in Italy, where the Kennewicketts and their robotic staff must face the perilous pigeon Iron Claw and Madini, leaders of the Mesmers, alone.

Will Wally, the noble boy scientist, and his daring dachshund, Noodles, be able to defeat the Mesmers and their minions a second time? Or will the darker side of the Kennewickett family line prevail?