OK, in one story, I have twin mad scientist kids (Tom and Joe) who are researching the supernatural, and they put out an add offerring to help people with supernatural problems (with the goal of finding research subjects). The protagonist (Jessie) contacts them because the past two full moons, she's turned into a wolf and mauled people, and she'd really like them to find a cure for that. Jessie remembers everything she does in wolf form, but can't control herself. It turns out she's got a spirit that's sort-of possessing her, though it's more of a symbiotic relationship than typical possession. (Most people with supernatural abilities in this world are either spirit beings or possessed by them.) Tom and Joe tell her that the first thing they should do is figure out why this possessing spirit of hers wants to maul people. Tom and Joe have encountered vampires before, but never werewolves. They've noticed that there are two types of vampires - the most common type burns up in sunlight, has superstrength, and can turn others into vampires; the other type can't turn people, has shapeshifting and subtle mind control, and is nocturnal but not seriously affected by sunlight (though it suppresses their powers). They are going to discover that the second type have a hereditary condition that attracts a certain kind of spirit being to gestate inside them. In life, they are werewolves, and once they die that spirit being mimics their appearance and personality, becoming the second subtype of vampires. As a result, Jessie's wolf form isn't actually interested in hurting people or in eating meat, but in drinking blood. If she gets a large amount of animal blood and sets it out in front of herself just before she changes, she'll drink that blood and be satisfied, and therefore be a friendly wolf instead of a vicious one. And if she doesn't get blood during her transformation, she'll get sick. I need advice on how to set up this revelation without making it too obvious. Tom and Joe will basically be discovering it scientifically, by making careful observations and running various tests on her. First clue is that both her previous transformations, she attacked someone, mauled them a bit, and then started copiously licking the wound, only continuing to bite once she ran out of blood to lap up. Second clue is that when she's just about to transform, locked up in a cage Tom and Joe set up for her, she smells a delicious smell. She doesn't know what it is, but Tom and Joe know that they have a mind-controlled vampire servant in the other room and he's drinking the blood they brought him. (They're not planning to tell Jessie this, and the reader isn't given any information Jessie doesn't have, but this is one of the big things that leads Tom and Joe to figure out Jessie's wolf needs blood.) Third clue is that once she's had a transformation without drinking any blood, she feels kind of tired and sickly for the next month, and it gets even worse for the second month. Do those first three clues make it too obvious, either to the reader and Jessie, or to Tom and Joe? Another thing - Tom and Joe pretend that they're ordinary kids who just happen to know about and have an interest in the supernatural, but they're actually possessed themselves, with a magic-eating spirit that has mindreading and mind control that only works on spirit beings. (Hence the mind-controlled vampire servant - though this mind control requires a lot of setup, so they can't use it willy-nilly.) They're careful to hide their quirks from Jessie, and this kind of spirit is hard for other spirits to detect (since it's a natural predator of spirit beings). But some small hints have shown up already. When they were trying to determine if Jessie's spirit generates electromagnetic waves (some, but not all, spirits do), both boys stood well away from the EMF (since they'd set it off). When they got Jessie to touch some spoons to see if she could distinguish the real silver ones from the fake silver (spirits are hurt by silver) they used latex gloves to avoid direct contact with the spoons. And a couple times they act like they know what she's thinking, although nothing that couldn't be explained by sensitivity to nonverbal cues. How obvious would those be? I'm not sure if I want to reveal what Tom and Joe are to Jessie (if she does find out, she's pretty much screwed, and I don't know yet whether I want her to have a happy ending or an unhappy one).
Doesn't seem to be all that obvious, no. AS LONG AS you don't make the clues obvious. In other words, don't make them seem important until the truth comes out. Where this is not possible - as with her sickness due to lack of blood - make it seem as though it's caused by something else (for example, give her the flu a short while after her unfruitful transformation to make it look like that's making her sick, but you should also make it clear that some things about her sickness aren't exactly adding up (some of her symptoms may not correspond with the flu). They could also later decide that - if you were to go with this idea - that she got the flu because of a weakened immune system caused by her not feeding on blood). Those are just my thoughts, anyway.
I have to agree with Temporal, the clues are not that obvious. However, I will deal with the 2nd and 3rd clue offerings. 2nd clue: throw down some misleading details. If she's locked up in the cage and smells something there is a possibility that maybe they'd had a takeaway delivered ... this may seem a little bit like a cop out, but when it's written down the chance that the reader will assume that it's the takeaway food that's appealing. Possibly. 3rd clue: werewolves change with the moonlight, not the taste of blood. Nit-picking, I know, but a simple observation.
She changes with the moon. But her kind are actually kind of a werewolf-vampire mix (a lot of the old legends had the two creatures overlapping a lot more than they typically do in modern fantasy). So she needs to drink blood during her transformation - not that it triggers a transformation (the moon does that) but that she gets malnourished if she doesn't.
