I can't truly judge what ideas as far as plot are inherently good and what are inherently poor, but I can break out the good ol' fashioned nitpicking. Chiefly, you need to focus more on your commas and grammar. I saw a few places in which you used the wrong 'your/you're', forgot apostrophes, and made a few mistakes in sentence structure, such as in:

"Waving his hands in disarray he spun on the spot and landed in his chair creaking its old joints and stretching the worn leather, it had seen better days."

This could be a good sentence to describe the chair, but the way you wrote it sort of disrupts itself. You could rewrite it as: "Waving his hands in disarray, he spun on the spot and landed in his chair. Its joints creaked and the leather stretched. It had seen better days." This way, it feels less like a run-on sentence. That's honestly the only advice I'd offer as far as grammar other than just proofreading everything and analyzing each and every sentence to be sure that little slip-ups won't tarnish the feeling of the piece and potentially pull readers away from the immersion.

Now, onto the meat of the advice: Good writers always know that it is better to take away from a piece than to add to it. Give the reader the absolute minimum for what you want to write. It’s difficult to express, but basically you must focus on the actions, the showing, and only a little on the telling.

Let’s say I write this sentence: “The man was very old.” Poor. Don’t tell the reader someone is old. Show them. “His face hung as a tapestry of wrinkles, and he hobbled about with a knobby cane.” That’s showing. 

Also be sure to avoid clichés in your writing, especially dialogue. “…as a smile stretched from ear to ear.” This is a little too much of a used phrase to really stick out in the reader’s mind. Don’t be afraid to get creative, get a little weird. Set the tone. Is the room the two of them in very dark? Is it gloomy? Is his smile disconcerting? Lopsided? Is he showing teeth? Are they rotten? 

Every sentence must be worthwhile. If it does not either advance a character or advance the plot, do not write it. A lengthy list of details that do not set the scene, the mood, or add anything to the text will bore your reader and make them skim over the important parts.

The boy dying is an interesting portion. You did a good job of having it come unexpected, but there was much you could have done to make it all the more jarring. “As quickly as a hawk would swoop, the old mans fingers had grasped his neck and dunked his apprentice's head into the sink of dirtied water. Muffled screams and splashing filled the room with an unsettling atmosphere.” This, especially at the end, tells too much and shows too little. Don’t just say the room was filled with an unsettling atmosphere. A good comedian doesn’t wait for the crowd to stop laughing before shouting, “That was funny!” Show how unsettling it was. Make the boy sputter, have it echo off the walls and into the shadows.

Also important: Increase the shock for your reader. Add little ‘cushion’ to the sentence, and make the action be read as quickly as you want it to be done physically. Let’s say a man is having a gun pointed at the head of his friend. The reader is on a precipice. Will his friend die? Shock your reader. “A hand tensed, and the gun fired.” For quick actions, use quick sentences. Make them pop, make them sudden, and don’t be afraid to do so. Some of the most well-written passages I’ve ever come across use short sentences just as often as lengthy ones.

Well, that’s about all I have so far. I hope this helps. Please, if you want any more criticism, let me know the specifics of what you want my opinion on and I will help as best I can. I also suggest going on Tumblr to look at some decent writing blogs such as “fixyourwritinghabits” and “fuckyeahcharacterdevelopment”, as well as just plain looking up tips, tutorials and the like online, there’s a ton of awesome resources from some really awesome writers. Good luck!