Marjorie Weinman Sharmat

"Nate the Great and his dog, Sludge, would like to take a break from solving cases. So they hide out in the woods. But soon they hear familiar voices shouting, "Nate the Great, where are you?" There are many mysteries to solve!"--

Nate the Great investigates the disappearance of a homemade pillowcase belonging to Rosamond's cat Big Hex.

Nate the Great follows the clues to find his lost dog, Sludge, in a department store.

Even a deep snow the week before Christmas can't keep Nate the Great and his dog, Sludge, from finding the special card sent to Annie's dog, Fang, by his mother.

Wealthy secret agent Olivia Sharp helps depressed Duncan find a friend.

Nate the Great and his cousin Olivia are on the case of a runaway turkey, but unfortunately the clues appear to contradict each other.

Nate the Great solves the mystery of the missing picture.

Nate the Great takes on his first night case and tries to solve the mystery of the garbage snatcher.

“I, Nate the Great, have something to say. My cousin Olivia Sharp is almost (but not quite) the world’s best detective. I solve mysteries. She’s an agent for secrets. You won’t forget Olivia. She won’t let you.”
Olivia sharp is back! Rather than solve mysteries like her cousin Nate, Olivia helps friends with their problems by detecting what’s wrong beneath the surface. You'll be won over by Olivia’s...

THE OWL EXPRESS
Nate, the great detective, and his dog Sludge, hit the rails on their latest case. Their mission: To guard an owl named Hoot. Hoot belongs to Nate’s cousin, Olivia Sharp, and she thinks someone on the train might be out to get her feathered friend. Then Hoot disappears! 
THE TARDY TORTOISE
The sun is shining, the birds are singing, and someone is eating the flowers in Nate's garden. A green tortoise is slowly stepping...