Hayley has withdrawn from the world and retreated into her shell ever since her police officer dad was killed in the line of duty a year ago. Hero is a young police dog who has been retired early - his handler was injured in the line of duty and he cannot seem to bond with anyone else. But when Hayley and Hero meet, two lost souls find one another. As they settle into their new lives, they quickly learn that old habits die hard when Hero is instantly onto a clue when the Whittaker Diamond is stolen. And Hayley is furious when DI Doyle, a former rival of her dad's, is assigned the case and immediately accuses ex-offender Dylan - an employee of her mum's catering business which offers second chances and rehabilitation. Can Hero and Hayley crack the case?