“Frequency” blends science fiction and family drama as John Sullivan, a New York City detective, discovers he can communicate with his deceased father, Frank, a firefighter, through an old ham radio during an unusual aurora borealis. They use this connection to alter the past, preventing Frank’s death and changing the course of their lives. However, their actions create unforeseen consequences, including the emergence of a serial killer that John must now stop with his father’s help across time.