What rank of policeman would handle a kidnapping case?

I'm helping someone edit a book that they wrote, and in this book, the father of the main character is kidnapped. Now, if someone reported a kidnapping, what rank of police officer would be in charge of the ensuing investigation? I realise ranks vary in each department, but in general, who would handle the investigation? The author of this book that I'm critiquing wrote that a police inspector would handle the investigation, but I'm not sure if this is realistic.