So I'm in the early stages of a 6 player DnD campaign. I wrote it myself and added a lot of content with a lot of room for PC's to do whatever they want within reason. I am having trouble reconciling one part of the early story in a satisfying (to me) way. Children have been disappearing from the kingdom, a local church was initially implicated. After some sleuthing and a little door kicking the players found that this was mostly a red herring. I have the main plot pretty embedded: Old royal family usurped long ago ancestors are secretly trying to usurp the current matriarch. Part of the reason for the missing children was to make an excuse for the kings some to be missing for which there is a large bounty. (So that players didn't immediately realize that the king was the main target).

TLDR: Lots of children going missing, need a compelling reason for this to take me and my players down a rabbit hole.

Thanks

If any of the party are small races (or they have strong contacts that are) they could very well be mistaken for children in a bungled kidnapping.

Have them meet a kid that helps them out of a bind. Give the kid a name, and the players will be invested in them. 

A couple questions:

• Why do the villains want to kidnap the king's son? How does this further their plot?
• What's the next step of their plan now that they have the king's son?
• What are the villains doing with the other children they kidnapped?
• Who's actually abducting the children? The old royal family is the mastermind, but who's doing the dirty work?

It seems like the main villains are going to a lot of effort to conceal their role in this conspiracy (at least for now), so perhaps they're working through some sort of intermediary. This intermediary might have another use for the other kidnapped children.

I'm guessing you have an answer to why the king's son was kidnapped. But here's a couple ideas about why the other children are being kidnapped and what's being done with them. Forewarning that these types of plots tend to be pretty dark.

• The children are mostly teenagers and are being recruited as soldiers or spies by the old royal family to help in overthrowing the current matriarch.
• The children are all magically gifted in some way (though just beginning to grasp their powers), and the royal family wants to use these abilities.
• The children's parents are being blackmailed by the villains in some way to help in the plot against the matriarch.
• The children are being given to the supernatural allies of the old royal family- perhaps hags or unseelie fey- who have other uses for them.
• The children are being sold as slaves and unless the PCs move quickly, they may be sent out of the country aboard a ship.

If you are looking for a reason for the children to be disappearing it depends on whether you want them found or vanished and dead or alive. Here are a few random ideas though

* Evil witch is catching them to eat(i.e Hansel and Gretel style) 

* Cult is kidnapping them as sacrifices or host bodies for evil beast thingies. 

*Human eating, intelligent monsters kidnap them to raise them in a controlled enviroment as "breeders" for a more sustainable. Basically livestock that wont fight back, since children can be raised to be more obedient than adults would be.

*Enemy is planning on murdering everyone in the city with a magical plague, but doesn't feel children deserve to die, so they are removing as many children as possible before the event. 

* A former hero came home from adventuring only to find his/her child was killed in a raid. This drove them to madness, and now they are kidnapping children who share features with their dead child and hiding them away in their country mansion. 

• Why do the villains want to kidnap the king's son? How does this further their plot? The ancient family usurped years before by the current monarch, is seeking revenge and the reclamation of the thrown. They have kidnapped the king's only heir to use his "king's blood" to create a new body for a Lich, plus the added benefit of killing the only heir to the throne which is the same as killing him in the short run. They will soon be attempting to assassinate the king to sow chaos in the kingdom to spring back into power.
• What's the next step of their plan now that they have the king's son? Kill the king, create the lich.
• What are the villains doing with the other children they kidnapped? The necromancers plan is to infect the children with some sort of plague and return them to the society to spread the plague to it's inhabitants to create a large amount of dead for the liches to be raised undead army.
• Who's actually abducting the children? The old royal family is the mastermind, but who's doing the dirty work? A necromancer who wants to create a willing lich body to host for an ancient demon.

I basically decided what I was going to do with the children, but there it is.

Thanks for your help, minus that Auberginian guy. what a c-word

If you want fun hooks, introduce a monster. I'm sure a Rakshasa would have all sorts of uses for children. And pulling the strings behind the kingdom to get what they desire is right up their alley