Benji, a stray dog who lives in an abandoned house on the outskirts of a small town, sets about his daily ritual of visiting human friends; he has no fixed home but he desires one, and he likes the children of the Chapman family, Paul and Cindy, best. Mary, their housekeeper, (Patsy Garrett) feeds him, but she knows that the children's father, Dr. Chapman, must not find out about him because he'll fire her on the spot. One day their father is about to appear, so they hide Benji under the table. After outwitting Dr. Chapman (Peter Breck), the children leave for school and Mary explains to Benji that Dr. Chapman stubbornly dislikes dogs, but he is a nice man. Continuing on his route, Benji chases a cat and greets Officer Tuttle (Terry Carter), who announces his wedding engagement and tells Benji that he, too, will soon meet the lady of his dreams. At Bill's Café, Benji wakes Bill (Edgar Buchanan) from his morning nap and receives a bone as payment. Returning home, Benji finds three suspicious characters, Linda (Deborah Walley), Henry (Christopher Connelly) and Riley (Tom Lester), breaking in. Although Henry and Riley are spooked by legends that the house is haunted, Linda intends to propose the location as a hideout to their boss Mitch (Mark Slade), mastermind of their illicit activities. Henry leaves a bag of groceries behind and Benji eagerly consumes an open pudding cup.
In Athens, Greece, a secret agent named Stelios goes to an outdoor café where the waiter gives him newspapers and a package. The newspapers reveal that a German scientist is missing in Greece and the package contains a photo of the dog Benji with his family. Meanwhile, in the U.S., Benji’s family arrives at an airport, on their way to the island of Crete in Greece. The children, Paul and Cindy, worry about their dogs, Benji and Tiffany, as they are placed in travel carriers. Cindy tells the airline representative that Tiffany has a “condition.” While waiting to check-in, Mary learns that the man behind her in line, Chandler Dietrich, is also headed to Crete. Dietrich then sneaks into the employee-only luggage area, snatches Benji’s carrier off a conveyor belt, drugs the dog, and imprints a code in his paw. Upon arrival in Crete, Dietrich befriends Mary, while the family learns that Benji and Tiffany missed the connecting flight from Athens. Stelios lurks in the background, watching.
On a rainy day in London, England, private investigator Benjamin Browning (Chevy Chase) accepts a ride from his gay friend, Freddie (Alan Sues), who is an erratic driver. As Freddie drops Benjamin near his office, the investigator collides on the street with writer Jackie Howard (Jane Seymour (actress)). When Benjamin asks her for a date, she tells him to contact her upon her return from Paris, France. Back at his office, Benjamin's secretary, Margaret (Barbara Leigh-Hunt), leaves for lunch, and a stranger named Quimby Charles (Richard Vernon), claiming to be a member of Parliament, proposes to hire Benjamin as a bodyguard for a friend, Mrs. Patricia Elliot (Marguerite Corriveau). Benjamin is reluctant, but Quimby offers a great deal of money. Benjamin accepts the assignment and goes to visit Patricia at her flat, where he discovers the door unlocked. As he searches the residence, decorated with artwork, he discovers Patricia dead on the bedroom floor, bleeding from a knife wound. Suddenly, an intruder fatally stabs Benjamin, steals Patricia's gold pendant and leaves.
Benji, the world's most popular canine actor, faces his toughest challenge yet. After a tragic sea accident, Benji is washed ashore in the rugged backwoods of North America, where he becomes the guardian to an orphaned litter of cougar cubs. Together, they dodge untold perils from man and beast in an amazing odyssey to reach safety.
The film starts with the understanding that the makers of the Benji (1974 film) are going to various towns in the U.S. looking for the next dog to play Benji. In a small Mississippi town, a freelance, abusive dog breeder named Hatchett keeps a backyard kennel under poor conditions behind his home. He lives with a young boy named Colby and his mother and is verbally and physically abusive to them, but Colby loves dogs and secretly nurtures a female black dog, Daisy, who is Hatchett's top breeder. He goes to an abandoned house in the neighborhood and takes food and water to the black dog so she can produce milk for her new pups. Hatchett learns of this and accuses Colby of stealing his most prize breeder, then orders Colby to take the black puppies, but abandons a fluffy, light-colored "Mixed-breed dog". Over several months, Colby secretly cares for the puppy, and he grows into the unnamed fluffy dog that will become Benji.