When a mysterious letter written in code arrives at King's house for his human, Kayla, he follows the trail of the person who left it.

Thirteen-year-old Ruby, a genius code-cracker and daring detective, gets an anonymous call setting a challenge that leads her to the headquarters of Spectrum, a highly secret anti-crime agency that needs her help to crack a code, but soon Ruby uncovers dastardly plans of the Fool's Gold Gang.

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.

It's no longer a game. The body count is rising. Shaken by recent events, Amy and Dan flee to a distant land and trace the footsteps of their most formidable ancestor yet: a military leader of mythic proportions. Yet just as the siblings begin to master the art of ancient warfare, they confront a dangerous enemy that can't be felled with a sword: the truth. With the stakes higher than ever, Amy and Dan uncover something so devastating it changes everything...

A million dollars, or a clue? Police report a break-in at an elite hotel, and the suspects sound suspiciously like Amy and Dan. There's a car and speedboat chase and an angry mob! When there's a Clue on the line, anything can happen.

As the race to find the 39 Clues builds to its explosive finish, Amy and Dan must explore an ancient culture and steal a Clue guarded by thousands of the world's best-trained soldiers. It's the most dangerous Clue search yet ... and it may mean the end for Amy and Dan.

An adventure on the wide open ocean, and Ruby is all at sea. Can she crack the case while evading the clutches of the evil Count von Viscount? Well, you wouldn't want to bet against her.

"Jacobite exile Mary Dundas is filled with longing--for freedom, for adventure, for the family she lost. When fate opens the door, Mary dares to set her foot on a path far more surprising and dangerous than she ever could have dreamed. As Mary's gripping tale of rebellion and betrayal is revealed to amateur codebreaker Sara Thomas, she faces events in her own life that require letting go of everything she thought she knew--about herself, about loyalty,...

Thirteen-year-old Dan Cahill and his older sister Amy race against time to find an ancient map that has not been seen for half a century and use it to redeem their family members who have been kidnapped by a sinister organization called the Vespers.

"An enigmatic message leads the Code Busters on a treasure hunt on creepy Alcatraz Island, where they must use their problem-solving skills to unravel the mystery" -- Publisher.