Day of Doom
The sixth and final book in the Cahill versus Vesper series, Day of Doom was written by David Baldacci, who for the first time with this novel, tried his hand at childrens literature.
Back of Cover
THE ULTIMATE SACRIFICE.
It started with a kidnapping. A shadowy organization known only as the Vespers snatched seven members of the Cahill family and demanded a series of bizarre ransoms from around the world. Thirteen-year-old Dan Cahill and his older sister, Amy, began a global treasure hunt, determined to bring back whatever Vesper One needed, so long as it kept the hostages safe.
But when they deliever the last ransom, Amy and Dan discover Vesper One's terrifying endgame. The objects he demanded are vital pieces in a Vesper plot tjat will harm millions of innocent people. Now the two siblings and their friends are in an all-out sprint to stop Vesper One...before the whole world goes BOOM.
Dan and Amy race around the U.S trying to find Vesper One's hideout while the weather is getting worse and worse, so bad it seems supernatural. They know they have to stop the Vespers or the whole world will go up in smoke.
But Vesper One isn't their only threat. Isabel Kabra is back, and on the same plane as the Cahills! But at the end she goes into butt-kicker mode and destroys Vesper One, a guy we never heard of before.