The Exploits of Neptune King is the fifth book in the series. In their first case our heroes tackle the supernatural, being hired to catch a vampire in Cornwall. In the isolated village of Abernathy, five young women are dead, their blood completely drained and puncture marks in their necks, and if that wasn't enough the locals are being scared by the spectre of a man that transforms himself into a bat. This is the sort of case that Neptune delights in. While Neptune is off sick, Rachel begs Shark to give her time off so she can nurse him back to health. Against his better judgment she convinces Shark to give her new friend Rebecca Evans a chance, leading to some volatile scenes thanks to her bad habit of conclusion jumping. Naturally she falls for him, and Shark finds he is irritated and attracted at the same time, but what could they possibly have in common? She, the daughter of an earl and distantly related to the Queen, and he the son of a drunken motor mechanic. Shark figures it's a relationship doomed from the start. They continue to go from strength to strength cementing their reputation as detectives when the tackle a case multiple murder where residents in a nursing home are being killed for their savings. Rachel goes undercover again as a nursing assistant, and breaks the case wide open, putting herself at risk