Frequency is a 2000 movie starring Jim Caviezel as "John Sullivan", and Dennis Quaid as "Frank Sullivan" (John's father). It has the fanciful plot of a father and son using amateur radio to communicate across time to prevent a crime.

The son warns the father (a fireman) about a warehouse fire that killed him 30 years ago. By saving his father, a new timeline exists whereby the mother (Elizabeth Mitchell playing Julia 'Jules' Sullivan) is murdered. The son (a New York policeman) and the father must work together to find the murderer and thus save the mother.

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