Darkness descends. Shadows creep and lurk in the far corners of his mind, solidifying into demons that prowl the halls of his mind palace. Razor-sharp claws drag against the carpets, ripping, tearing; twisted, malformed bodies slink along, their staggering gaits echoing in the silence that always descends when they come; glittering, wide black eyes scan for his weaknesses, and upon finding one, shrieking, piercing cries of demented glee ring out.
They sink their claws and fangs into the weak spots and pull and rip and tear, eating, devouring, taking their fill and more until their stomachs are distended and gore dribbles down their chins. His mind is theirs.
They move to his heart, a place once possessed by a good man, a kind man, so wonderful. Now, it is laid waste, broken and crushed and all but dead in his chest. The good man had gone, left, and a latticework of pain and loneliness has twisted over the muscle, binding it to stillness. That's alright. They can bite through that too. Though bitter and cold, it still tastes good enough for them to finish it off, leaving only a tiny portion to sustain him as they finish their meal.
The soul can be a beautiful thing. Bright, shining, the core of a person, their essence. Not this soul. This soul is scarred, burned by cocaine gouged by love lost. This soul is dulled and grey, listless. It is shrunken in on itself, cowering; it has seen these demons before. They used to come often, only to be chased away by the heavenly fire of drugs. Now, the heavenly fire has turned to hellfire that spurs them forward, makes them laugh and scream in perverted delight as they take their meal.
A needle falls, glass shatters, and a man falls close behind. Icy eyes are frozen open, awake in death. The demons laugh as they slink away for the final time.
The mind ate the heart, the heart ate the soul, and the drugs ate the man. Thus was the life of Sherlock Holmes.