The shadow of the man in black has followed fourteen-year-old Amy Cahill and her younger brother Dan on their worldwide search for 39 Clues that lead to a great power. The man has tried to kill them and he is a Madrigal, as were their parents. And now the man is ready to step out of the darkness for their final confrontation.

Chronicles the first Vesper attack on Jan van Eyck's altarpiece at Ghent in the 1600s, then jumps to WWII and young Grace Cahill's desperate bid to save the masterwork from the Nazis.

Dr. One-Zero won't stop until the whole town--no, the whole world--embraces the "true happiness" found in his poisonous potion, Green Pop. And now that he has the Turtle of Light, he's virtually unstoppable. There's one weapon that can defeat him: another Turtle of Light. Unfortunately, they can only be found in another dimension! To open a portal to this new world, Hopper, Eni, and Josh's coding skills will be put to the test.

657 days ago Meg's British father left their home in France to fight the Nazi's, leaving some codes in a jar for her to decipher, and Meg and her French mother moved to the Perche, a region in France near Normandy known for its forests; now Meg watches the German soldiers in town, and sometimes carries messages for the French resistance--but suddenly things have gotten much more dangerous: there is a wounded British officer hiding in her grandmother's...

Thirteen-year-old Ruby Redfort is an undercover agent and genius codebreaker.

After twelve-year-old Addison Cooke's uncle unearths ancient Incan secrets in Peru, he is kidnapped by a shadowy organization intent on stealing the treasure unless Addison and his friends can decipher the clues first.

Unexpected media attention in their Harlem neighborhood bring Shelby Holmes, nine, and John Watson, eleven, a new case that sends them undercover as figure skaters.

In 1666, after four months away, friends Christopher Rowe, Tom, and Sally return to London triumphantly but, guided by coded riddles, face a conspiracy that threatens Christopher, as well as the King himself.

"Cruz and his fellow recruits tackle challenging missions to dispense life-saving medication to gorillas, thwart pangolin poachers, and capture images of the last known cheetahs in Namibia--all the while discovering that protecting the world's threatened species is a dangerous business. Things turn deadly for Lani, Sailor, Emmett, and Cruz as they search for the fourth piece of Cruz's mom's cipher. Cruz knows it's not going to be easy, but will an...

Kiki and her friends learn about coding as they compete to be the escort for young narwhal who will visit Trident Academy with her famous parents. Includes glossary, key to the codes used, and information about safeguarding narwhals' habitats.