Beethoven (1992)

Storyline:
The Newton family live in their comfortable home, but there seems to something missing. This "hole" is filled by a small puppy, who walks into their home and their lives. Beethoven, as he is named, grows into a giant of a dog... a St Bernard. Doctor Varnick, the local vet has a secret and horrible sideline, which requires lots of dogs for experiments. Beethoven is on the bad doctor's list.