The Black Net — Steven Bannister

 DCI Allison St Clair has cheated death- but only just. She is weakened and desperately needs rest. But something calls to her from ancient Cornwall where a sickening wave of bizarre murders has local police well out of their depth. The problem is, they just don't know it. 

 She must somehow halt the killing spree. But how? A London-based Detective Chief Inspector no matter how talented, has no jurisdiction in Cornwall. 

 Revelations from Cornwall's deep past are uncovered during the Midsummer Golowan Festival- a gathering whose primeval rituals and bonfires have been badly misunderstood. Human frailty has opened the door for the insidious Mister Black and The Game takes on a new, deadly twist and this time, on a mountain floating on a black sea, the future of humanity will be decided.