Songs in a Box

This time, the enemy is human.
On a trip to spread his Grampy's ashes in the Amazon, John "Lockjaw" Smith finds love, and a renewed sense of purpose, in the person of Willa Vernon, a lady haunted by her past association with a group of eugenic maniacs.
On the return trip, they add a passenger. She is a delightfully unique "ninety-year-old hyperactive child" with eyes like a jaguar, muscles like a howler monkey, and the mind of the Savant. She names herself Dorothy, after the fictional balloon traveler to a place called Oz.
Dorothy knows the world only from stories, yet she is the only person alive with the ability to save the world from Willa's old employers. She has thirty days to solve a puzzle.
The maniacs have a head start of more than a century. It's not fair. Poor maniacs. Oh, well. A little mass murder could even the playing field again.