A succubus is stalking the streets of Preston. But she's not just giving certain young men erotic dreams: she's leeching the life out of them. With Detective Chief Inspector Alf Stone still on paternity leave after the birth of his son, it's down to DI Alexandra Johnson to investigate. But why are all the victims called Ryan? And how on earth do you bring an entity to justice? With the help of young witch Mary Conway, the newly formed 'Unusual Investigations' team of Ratcliffe and Kat, her new sergeant and a computer whizz of a PCSO, Johnson begins to unravel a web of intrigue that goes back fifteen years. Then Stone returns and starts digging into a cold case...