In the quiet Massachusetts town of Edgefield, a pair of bumbling kidnappers break into the house of wealthy Mr. Flint, intending to kidnap his wife and hold her for ransom.

Patti Randall is a troubled teenage girl struggling with the mundanity of her everyday life, and the fact her parents dislike the way she behaves and dresses.

Seizing her chance, Lizzie attempts to scratch "HELP" on her watch, but stops with the last letter incomplete (resembling a second "L") when the kidnappers' phone rings.

Determined to take advantage of the exciting situation and save Lizzie, Patti goes to Boston and pleads her case to Agent Zeke Kelso of the FBI, who believes her.

As she walks towards her house, Patti notices D.C. digging in a garden; he runs off, and she follows him to the kidnapper's hideout, finally discovering Lizzie's whereabouts.

Patti calls Zeke for help insisting her cat finally found the kidnapper’s location, but he is still upset with her and refuses to listen and believe her.

D.C., Patti, and Zeke pursue them through the town, but due to an earlier sabotage caused by competing mechanics, the kidnapper's car can only turn left, hindering their escape.

D.C. rallies the show cats to run with him along the roofs of the neighborhood and jump down onto Ma and Pa's car, causing it to crash, foiling their crimes.

Ma and Pa are arrested and charged with kidnapping, Lizzie is reunited with the Flints, and Patti and D.C. return home and are hailed as heroes.

[10] Stephen Holden of the New York Times was not impressed, remarking: "The opening scenes in That Darn Cat suggest that the movie might have found a gently sarcastic attitude in tune with the know-it-all mood of the late 1990s ...