The clue comes from the psycho Raimy talks to in prison. He's a physicist, and claims he's connected to his own future self - via a device he built. Other than the mad-scientist, homicidal aspects of this guy, can we take his story seriously and does the machine he says he built for himself have any connection to Raimy's?
Possibly on the first question, no information on the second. The mad scientist seems to have knowledge of value to Raimy. Whether it came from the machine he wants to rebuild is not clear at all.
But introducing this new character is a good move in our story, because it takes the connection between Raimy and Frank out of the incredible quirk category (the movie's "explanation") into what may be something much greater, with who knows what consequences.
This is more important than the mad scientist's talk about not being able to change the course of history by cutting off a branch from the tree, because the tree will just put up another branch, which means that the only way you can change history is by cutting the tree down - sawing it off at the trunk. This makes sense enough, but leaves open the question of what, in any situation, is the branch and what is the trunk?
Frequency the television series continues to be an enjoyable time-travel narrative - via trunk and branches. May it thrive.
See also Frequency 1.1: Closely Spun Gem ... Frequency 1.2: All About the Changes ... Frequency 1.3: Chess Game Across Time ... Frequency 1.4: Glimpsing the Serial Killer ... Frequency 1.5: Two Sets of Memories