Five kids are taught the invaluable lessons of bike safety by bike safety wizard Sam Sprocket.

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.