I'm writing an adventure for my group in my GURPS Space campaign. The characters have joined a detective agency, and will be assigned to solve the mystery of a theft of an important jewel from the Royal Family of a distant planet. I've got a few of the details sorted out, but I'm struggling with how to lead the players to the culprit without it being too obvious. The King has recently died, and his eldest child is his daughter, who needs the diamond to secure the loyalty of her people to become queen. Her younger brother has stolen the diamond in his attempt to jump the queue to the throne. If successful, he will leave the galactic federation, so the stakes are high.

The jewel is smuggled out of the capital in the King's corpse, which is making the rounds between cities so his people can pay their respects. Once the players figure out they need to travel to another city, where the Prince lives, they will be subject to a sabotage of the vac-tube system, stranded in the middle of nowhere, where they will come across a secret military depot for forces loyal to the Prince. They'll probably attack the base, and win, and travel on to the city where the Prince lives.

Bits I'm stuck on:
How do the players figure out to travel to the city where the Prince lives? Do they suspect him too early (i.e. is it too obvious?)
Who else would they suspect, and how would they rule them out?
How will they discover the hiding place where the Prince has the diamond, again without being too obvious? (I've worked out the scene when they get there)
How do they get back to the capital with the diamond without getting caught? (Maybe they're chased?)

Any suggestions very welcome! Even just very brief idea snippets will help.

Cheers

First let me say good luck running a mystery.  

Second, they way you have it sketched here sounds like a rail road.  Expect to take a huge amount of flack for that.  "We don't take to kindly to railroads round here."

It might be mitigated by thevfact you are running a mystery, its kind of necessary for a mystery.  

K now to some tips.  

You need Personna Dramatis.  A list of a dozen movers and shakers that are invested in the out come. You might even hand the list and short Bio to the players in session 1.  

Don't hide any clues behind skill checks.  You don't want to end up in the situation where if they fail a roll the adventure stops.  

3 clue rule.  This one I am stealing from someone else on here, if they miss one clue there needs to be another one behind it they can find.

As for getting them on the train, you can always attack them.  Then either plant a clue.  Or flee onto the train.  

Last bit.  If you plan scenes I think you are setting someone up for frustration.  No plan surivives contact with the PCs.

Good luck.  
Welcome aboard.

Another idea is to make sure there are several possible solutions and several ways to get to the solutions, otherwise when you fixate on "the butler did it" and there's one clue that proves it, you may end up with frustrated players who miss what you think is obvious and piece together another solution that makes sense to them.

You seem to have a predetermined  outcome in mind.  Players rarely stick to script.

Thanks for the feedback - it's quite helpful. I'm already thinking up a few alternatives.

Cheers!

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