Quickleaf
Legend
I just couldn't stop reading your whole story. That sounds amazing. I love how you subverted the player's expectations of a lycantrope with the silver necklace, and managed to surprise the players regarding the true villain, and the nature of the curse. I also love how you turned the library investigation into a puzzle + combat encounter.
I think one of the most important things about a good mystery, is to second guess what your player's assumptions are going to be, so you can subvert those assumptions, while still guiding them towards the important revelation without them feeling they are being guided.
In the end all of the subtle clues do need to make sense. There has to be this moment where your players go "Oh, I get it!", and that is ultimately the most fulfilling moment of any mystery adventure.
The way I foreshadow things, is by making sure that at the start of a session there is an event or remark by a character, that is seemingly unimportant. But as the story unfolds, eventually it all builds up to a big revelation.
Yeah, when it comes to the subtle hints building on one another I've learned that presentation can be equally important as preparation; just ran a one shot (it's been a while since we did a face-to-face game) where my choice of language and intonation made all the difference in the world to the players recognizing that, yes, this is indeed a clue worth paying attention to.