Skase investigates an ex-informer's love life in his hunt for clues to a series of arson attacks which have been left unsolved following the swift departure of DS Pearce. When she offers the identity of the arsonist in return for getting her boyfriend off the hook, Skase suspects that she is simply toying with the police in order for her boyfriend to receive immunity. However, when another fire breaks out, Skase realises she may have been telling the truth all along.