I agree with the last reviewer, this has the feel of an Agatha Christie mystery, albeit on the violent side.
Series director Walter Grauman did an excellent job, especially with a dog as the central character, as you will see.
Buck, the dog in question, is held reponsible for killing a boy's stepdad, though the catch here is the belief the dog was trained to kill. Homicide 101.
The campy aspect of the actual killer blowing a dog whistle in the bushes is one to see, and still frightening after all these years. An example of top storytelling.
One dynamic cast at play, lead by series regular Claudette Nevins (as Claudia), popular film actress Ina Balin (the GREATEST STORY EVER TOLD) as Laura and Roger Perry as Dan. Roger was everywhere on tv at the time, and must have had a marvelous agent!
Can you guess whodunit by midway?
This may have been inspired by an early season episode of CANNON, the one about an embittered war veteran who employed a killer Doberman. The writers of COLUMBO also picked up on this idea for one of their episodes (How to Dial a Murder), which was one of the most violent for that series and is not always rerun for that reason.
The very best from SEASON 4 EPISODE 10 remastered CBS dvd box set.