Why am I scared of the dark after a nice Sherlock Holmes reread

I need to stop reading Sherlock Holmes stories at one o'clock in the morning. Every time it happens, I end up convinced there's something sinister lurking in the dark right behind me. This means I can't possibly leave the circle of light around my reading lamp, which means I have no choice but to keep on reading. 

Is this an attempt to justify reading all night? Yes it is. But genuinely, it is ridiculous that even though I've read all of Sherlock Holmes before and I know how the stories end, they still creep me out if I read them in the dark.

It's not as if mysteries are inherently scary - I mean, sure, blood and guts and murder, oh my, but there's an entire genre of cozy mysteries proving those things can be quite soothing in the right context. If a crime novel has people turning up dead in a cheery little village, my feelings after reading the book will be along the lines of 'that felt like a nice vacation in a cheery little village.' It takes a little extra on top of murder to be truly alarming - a particularly unsettling manner of death, for example, or sinister threats and warning signs. Something to give me the creeping sense that danger is moving through the shadows, drawing in around me, etc. etc.

This is where Sherlock Holmes excels. All the murders (and lesser crimes) are laden with frightening trappings - mists and old crumbling houses and long nighttime vigils and women fainting dead away when mysterious men arrive out of their pasts bent on revenge. It makes me start to think what a dark world we live in for such things to happen, and just like that I'm huddled over my book, wondering if there are monsters under the bed.

What I need to do is defang the beast - reduce the terror to the sneaky rhetorical tactics it actually is. If I can figure out how exactly the Sherlock Holmes mysteries manage to be so frightening even after many rereads, maybe next time I’m suffering from murder mystery-induced insomnia I'll be able to tell myself it's just very clever writing, now turn off the lamp and go to sleep. So without further ado here are the top five tactics I've seen used in Sherlock Holmes to turn up the fear.

1. Time stamps.

If a story names a specific year and season and time of day, I'm immediately thrown into an apprehensive mood. This day was memorable enough for somebody to write it down. Therefore, something big is going to happen on this very day. Since Watson is always starting his narration by describing when exactly Holmes took the case, I tumble into every story already nervous. 

The effect intensifies when the time stamps go hour by hour instead of day by day. If I see a phrase like 'By eight evening, I was restless with anticipation' or 'The clocks had just chimed an hour after midnight' I go right to the edge of my seat, because I know if we're talking specific clock times the action is about to happen now.

2. People keeping secrets.

Waiting for a jump scare is worse than getting scared. It's the not knowing - it leaves my mind free to fill in the blanks with all kinds of horrors. The Sherlock Holmes stories like to play on this little piece of psychology by hinting that this or that character is hiding something. It might be innocuous, but as long as I don't know what secret they're keeping, I'm likely to imagine all kinds of horrors. They're probably not a raging axe murderer, but do I know that for sure?

3. Attention to irrelevant but poignant details.

Watson is always taking a break from the facts of the case for asides about the cold weather outside, or the bleak landscape, or the late hour. None of it actually dangerous, but all of it reinforcing the feeling of being alone in some isolated place with evil abroad. Also, a sudden digression into setting a dramatic scene is the strongest possible signal that something is about to go down.

4. A trusted character being frightened.

This one only works because I've become well acquainted with Holmes over many cases and I know he's pretty unflappable. Other characters may panic all they like, but if Holmes shows signs of alarm, things are getting serious.

5. And if all else fails: good old-fashioned Gothic horrors.

Here's just a sampling of the melodramas and grotesqueries featured in Sherlock Holmes: feral animals from baboons to mongooses to snakes; green glowing slime; eerie noises drifting through the mists; ancient manor houses; cryptic signs and symbols (preferably written in blood); disfiguring terror on the faces of murder victims; and travelers from far off lands. Especially Americans! So terribly gauche and brash because they were brought up in some barbaric land called California.