Tanith Lee 
To Indigo 

Don’t talk to strangers. Don’t even look at them. The life of Roy Phipps can be summed up in a paragraph: He’s fifty, leads an uneventful, well-organised existence in the house inherited from his parents, earns a modest income writing formulaic detective novels, and remembers, sometimes, his encounters with women. Roy’s only aberration is the other novel he has been secretively also writing for years, the sprawling and florid story of the mad poet Vilmos, a study of murder, angst and alchemic magic. Then one evening Roy meets Vilmos, face to face. Of course, handsome Vilmos’s double, Joseph Traskul, is only a coincidental look-alike. But in those fatal minutes a terrible bond is formed. For Traskul is, at the very least, insane – charismatic, predatory, lawless – a sort of human demon – whose almost supernatural powers, once provoked, will prove unstoppable. As the fiery shadows close in on him, Roy soon understands that he is now fighting for his own sanity. And probably for his life.