Marjorie Weinman Sharmat

While traveling on the train to San Francisco with his cousin Olivia's owl, Nate the Great and his dog Sludge must use all of their detective skills when the owl suddenly disappears.

When he finds a torn piece of paper with only part of a word on it, boy detective Nate sets out to find the missing pieces.

Nate the Great goes to San Francisco to solve a mystery with his cousin, Olivia Sharp, who is also a detective.

Nate the Great: "When Nate gets an urgent call from Annie about a lost picture, he immediately plunges into his new and baffling case with the cool detachment of a Sam Spade. Nate, the boy detective who likes to work alone, solves the mystery and tracks down the culprit. In the process, he also discovers the whereabouts of Super Hex, the missing cat"--Publisher. Nate the Great goes undercover: "Nate the Great has his first night case! Somebody is...

A New York City boy's preconceived ideas of life in the West make him very apprehensive about the family's move there.

E.J. the spy tries to uncover a secret that Olivia is keeping for a client.

Wealthy Olivia Sharp, agent for secrets, uncovers several secrets on a trip to Carmel, California to help a friend become a member of an exclusive club.

Olivia Sharp, cousin to super sleuth Nate the Great, is a detective too! Rather than solve mysteries like Nate, Olivia helps friends with their problems by detecting what's wrong beneath the surface. You'll be won over by Olivia's spunk, eccentricities, and can-do spirit.
THE PIZZA MONSTER: Meet Olivia Sharp. She's bold. She's eager to help people. She's a special kind of detective. She's an agent for secrets. Duncan is Olivia's first...

Fred Shedd and his parents accompany their dog Duz to Hollywood, where his new career as a movie star is almost ended before it begins when Duz is kidnapped.

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...