At the edge of the Pennine Moors, Detective Sergeant Blackshaw and his rookie colleague, Detective Constable Lumb, are called to the scene of a double murder committed on a burial ground.<br /><br />They discover that the case is connected to an ancient Celtic cult, in the remote village of Pen Crags.&nbsp;Desperate for career advancement and obsessed with solving the mystery, DC Lumb immerses himself in the group - and soon disappears.<br /><br />Amid a chain of unexplained deaths, Sergeant Blackshaw attempts to&nbsp;unravel the sinister plot. But with scarce evidence, can he prove his theory - or will he have to accept that there is no way to catch a phantom?