Whoosh! The animal catcher's net scoops up a stray alley cat in a lonely downtown alley. Locked in a cage in the city pound van, the spunky alley cat vows to get away. The van hits a bump on a steep San Francisco street, and the door to the alley cat's cage jiggles loose. When the van stops to pick up a lost hound dog, the alley cat makes a gutsy escape. In the middle of the night, Dan and Catrina hear noises outside their house. A burglar? Dan finds a cold, scared, wet "cat burglar" cowering in a corner of their window well. Because the cat is so hungry, Dan and Catrina nickname it Starvin' Marvin. The name sticks, even though they later learn the cat's a female. They quickly fall in love with Marvin and keep her.
Everyone in the neighborhood loves Marvin. Everyone except Nosy Nellie, the snoopy 82-year-old lady who lives next door. The spry woman with the long, gray braid gets her nickname because "when it comes to business, Nellie's more interested in other people's."
Trouble doubles when Dan and Catrina bring home another cat that looks just like Marvin. The cat is so thin they name her Skinny Minnie. They adopt the loveable new cat "so Marvin can learn to be a house cat." When Nosy Nellie learns about it, she plots to cause trouble and force the cats out of the neighborhood - but not before she gets San Francisco's Good Neighbor Award.
But while Dan and Catrina are at work, a burglar sneaks into an open window. But something scares him, and he dives out the window, breaks his leg and can't run away. The police capture him but they don't know how it happened. But Nellie does. She sees the whole thing.
Later that day, Marvin and Minnie jump outside through a window and climb along a tree branch over the sidewalk. Meanwhile, Nellie's other neighbor, Janet, pushes a stroller with her sleeping baby Andy. But Janet trips on the steep sidewalk, and Andy's stroller comes out of her grip. It races down the sidewalk toward the busy street. Marvin and Minnie save baby Andy. Janet doesn't see how it happens. But Nellie does. She sees the whole thing.
While Marvin and Minnie hide in Janet's backyard, a fierce storm looms overhead. Lightning strikes a pile of cardboard moving boxes stacked in the yard and starts a roaring fire. The cats are frightened and run toward their home and through the open window at Dan and Catrina's house. On the run, Minnie turns on the lawn sprinkler, and water soaks the bonfire of cardboard boxes. The flames go out just as the fire trucks arrive. The fire fighters don't see how it all happened. But Nellie does. She sees the whole thing.
Nellie has a few surprises of her own at the Good Neighbor Award. But the biggest surprise is on her! With Marvin and Minnie, anything is paws-ible! Are Marvin and Minnie common cats or American heroes? Nosy Nellie knows the answer.
