Orphans Amy and Dan Cahill, continuing their worldwide quest to track down the thirty-nine clues that will reveal the secret of the Cahill family's power, follow a link to one of the planet's strongest fighters, and have a run-in with the unreliable Alistair.

When a mysterious stranger makes their father an offer to fix the clock at Blackford House, Lucy and Oliver Tinker join forces with the magical clock animals to defeat a vicious monster, who wants to take possession of the house.

Neptune, King of the ocean, sends half-mermaids Emily and Aaron to the land of the midnight sun to investigate the source of the dangerous storms brewing in the ocean.

Schoolgirl detectives Daisy Wells and Hazel Wong are at Daisy's home when someone falls mysteriously ill at a family party, but no one present is what they seem so the Detective Society must do everything they can to reveal the truth.

In an early nineteenth-century alternate-universe, brusque eleven-year-old genius Ada and romantic fourteen-year-old Mary form a detective agency and investigate a stolen heirloom using their math, science, and analytic talents.

Someone at school keeps stealing the sandwiches from Marin's lunchbox, and he is determined to find the culprit.

Detectives' Row is full of talented investigators, but Toby Montrose isn't one of them. He's only an assistant at his uncle's detective agency, and he's not sure he's even very good at that. Toby's friend Ivy is the best sleuth around -- or at least she thinks so. They both see their chance to prove themselves when the famed Hugh Abernathy announces a contest to choose the World's Greatest Detective. But when what was supposed to be a game turns into...

In 1940, during the Blitz, Kat Bateson is sent to a school in a Scottish castle that is said to be haunted by dark magic from the past, but when some of her classmates disappear, she wonders if the magic exists very much in the present.

What would happen if you discovered that your family was one of the most powerful in human history? What if you were told that the source of the family's power was hidden around the world, in the form of 39 clues? What if you were given a choice - take a million dollars and walk away ... or get the first clue? If you're Amy and Dan Cahill, you take the clue - and begin a very dangerous race.

Hank the Cowdog, Head of Ranch Security, is framed for the murder of a chicken and becomes an outlaw with the coyotes.