When Dr Harrison Lane, head of the Ritualistic Behavioural Crime unit, is called to a remote Yorkshire cave, he finds a horrifying scene of murder. The victim, wearing the mask of an Egyptian deity, is found amid flickering candlelight and symbols painted in blood on the cave walls.

The terrified witnesses talk of growling spirit mists and a killer they couldn’t see; and as Harrison works to unravel the symbolic clues, his worst fears are soon realised.

When another person falls victim to the ancient curse, it’s clear that the group of university students who practised forbidden rituals here three decades ago are now the targets of someone’s deadly revenge…

As the group members are picked off one by one, Harrison knows time is running out. Can he separate fact from fantasy before the killer’s deadly rite reaches its finale?