Where there's a will, there's a wag
Marilyn Singer
Philip Barlowe, bumbling detective, and Sam Spayed, his intelligent dog, are hired to investigate the will of a woman who has left her vast wealth to her cat.

by Joan Lexau (1985)
When his neighbor finds dog food in strange places all over his house, Willy Nilly asks Miss Happ, a witch, to help solve the mystery.
Marilyn Singer
Philip Barlowe, bumbling detective, and Sam Spayed, his intelligent dog, are hired to investigate the will of a woman who has left her vast wealth to her cat.
Carolyn Keene
Nancy tries to find out who is trying to sabotage the International High School Track and Field Games before it is too late.
Donald J. Sobol
Leroy Brown is back in the next six books in the Encyclopedia Brown series. As Idavilles ten-year-old star detective, Encyclopedia has an uncanny knack for trivia. With his unconventional knowledge, he solves mysteries for the neighborhood kids through his own detective agency. But his dad also happens to be the chief of the Idaville police department, and every night around the dinner table, Encyclopedia helps him solve some of the most baffling crimes. With ten confounding mysteries in each book, not only does Encyclopedia have a chance to solve them, but readers are given all the clues as well and can chime in with their own solutions. Interactive and funits classic Encyclopedia Brown!
Joan Lowery Nixon
Sixteen-year-old Mary Elizabeth's summer job at an expensive health club turns out to be more exciting than she bargained for when a series of mysterious events culminate in murder.