The Randall sisters, Patti (Hayley Mills) and Ingrid (Dorothy Provine), never have a dull moment, thanks to the antics of D.C., their trouble-making Siamese cat. When D.C. wanders into an apartment where bank teller Margaret Miller (Grayson Hall) is being held hostage, the clever captive writes “help” on her watchband and attaches it to the cat. Upon finding the message, Patti and Ingrid contact the FBI, and soon agent Zeke Kelso (Dean Jones) is there to investigate.