Jack and Annie travel 500 years back in time to Florence, Italy, and spend a day helping Leonardo da Vinci in the hope of learning another secret of happiness. Jack and Annie are on a mission to save Merlin from his sorrows! The brother-and-sister team travel back in the magic tree house to the period known as the Renaissance. This time, Jack and Annie will need more than a research book and a magic wand. They'll need help from one of the greatest...

When these ducks go to the pond, it is Bim, Bam, Bop . . . and Oona, always last. They're all ducks, but Bim, Bam, and Bop are runners, and Oona's a waddler. "Last is a blot on my life," she says to her frog friend, Roy. "I don't feel as big as a duck should feel." But she's good with gizmos, Roy reminds her. So Oona tinkers with things, scraps, and strings, and eventually creates just the right gadget to get her to the pond first. Spunky Oona will...

On the ocean liner Mauretania, two European scientists with a dramatic new invention are barely rescued from abduction by the Van Dorn Detective Agency's intrepid chief investigator, Isaac Bell. Unfortunately, they are not so lucky the second time. The thugs attack again-and this time one of the scientists dies. What are they holding that is so precious? Only something that will revolutionize business and popular culture-and perhaps something more....

1666: Two monks at the monastery of Andechs experiment with cutting-edge technology, including a method of deflecting the lightning that has previously set the monastery ablaze. When one of the monks disappears and his lab is destroyed, foul play is suspected. Who better to investigate than the famed hangman Jakob Kuisl?

When Rosie is unable to invent a contraption to help one of Aunt Rose's Raucous Riveters friends, she calls on classmates Iggy Peck and Ada Twist to help.

It is August 1899, and Thomas Edison proclaims his most amazing invention yet: the Spirit Phone Model SP-1. At nearly the same time, a cocksure young mage named Aleister Crowley inexplicably teleports into the home of Edison's archrival, renowned inventor Nikola Tesla. As insanity and suicide multiply among spirit phone users, Crowley and Tesla combine their respective skills in "magick" and technology to investigate the device's actual origin and...