I'm trying to write this campaign for a group of my high school buddies that will be returning from college this week. One of the players is in my main campaign that's going through all the written material, so I need to write up my own campaigns so he doesn't have to play the written stuff twice. I was trying to think of a way to have the guy who plays in both start the game as a radical psyker and as the game progresses, he gets more and more radical and others start to notice, at which point they must either turn him in, or join the radical forces. I'm pretty new to Dark Heresy, and GMing in general so I'm wondering how this would work. I have the Radical's Handbook as well as most every other book... Any suggestions or ideas?

No need to push such a thing.

You simply try to keep the party nice, honest and puritan, while making it clear that the easy way out is using a xeno/chaos weapon.
A psyker, in my experience, will be radicals almost by definition...

Of course, I tend to play either Monodominants or Xanthite characters...

Depends on your players, but I'd be careful with pushing it, other players may resent it. As Harboe suggests, I'd let it organically develop. Leave the weapons of the enemy laying around, and some PC's are going to pick them up and use them.

Thanks for the feedback guys! I'm new to the whole GMing scene so I still have a lot to learn. I'll see if I can leave a few Xenos weapons or cursed items for them to pick up...

This is something that I am having to be careful about.

All of my players know I have just acquired the RH and I have waved it under their noses in order to try and draw out some radical tendencies. However, they are not taking th bait and want to remain 'pure' despite all the new character options.

If I start thrusting radicalism down their throats they are just going to feel rail roaded because the GM has a new book that he wants to use.

As suggested by others I plan to in some temptation as naturally as possible and I also feel that the new addition to the corruption rules should help them along the radical path. After a a long greak due to having a new baby the guy who plays the psyker is returning to the our group in 2010 and I have found that having a psyker in the group eventually damns them all to hell anyway making the use of the new material all the more alluring.

Does anyone think we will get a Puritan's sourcebook, or is this pretty much covered by the vanilla Inquisition template as put forward by the core rulebook?

To give you a tip from the horse's mouth:
"(...) where they stand, ideologically, and of what they will and won't do. Now to start pushing them. (...) You can start the path to Radicalism quite innocently. As part of an investigation, present them with a dubious source, a source who acquires excellent information that has been obtained from a rogue psyker (...). What will it take for the Acolytes to use the source again? How much will it take to push them to bypass the source and go straight to the rogue psyker? At what point to they dispense with the psyker entirely, and begin to make use of similar powers themselves?"
(Hope I'm not quoting too much for any [copyright-related] comforts. It's Radical's Handbook, p. 222)

If the group won't use Chaos-tainted weapons EVER, then don't just throw down a kickass Chaos-tainted sword and wait for them to take it. Make them have to read that Chaos-tainted tome that'll tell them where the cultists need to strike to get their next sacrifice. Have that book contain the knowledge on how to bind a daemon into a sword (perhaps that's what the cult is gathering sacrifices for? Also allows you to hand out a little extra corruption for that forbidden knowledge).
Later, when faced with an antagonist who's clearly too strong to deal with on their own they'll have to find a way to prevail. Maybe they won't do it to save one person (even another PC), but how about 10? 100? 1000? A planet? A star system? A subsector? A sector? A Segmentum? The entire Imperium?

You can even present a likable Radical, if you fancy that. Someone who openly admits to being damned for his methods, but saying something to the effect of: "Even if I am tainted by Evil and may never live to see the Good I've nurtured and protected, it's is what must be done to save us all. I don't expect the Emperor to have mercy on me and I won't ask Him for it, but I would have failed my duty if I did not fight the enemies of Mankind with all I had."

Harboe said:

Actually, that sounds a bit like the Oblationist philosophy, though they're more dour about it.

Upbeat and he's a Xanthite.

numb3rc said:

True.
Were you looking for Xanthite?
"It's the natural progression of things. Man even feared fire before we mastered it. It amazes me that we in an age where billions of people are travelling between the stars at any given time that this irrational fear of the Immaterium has become so widespread. You talk of daemons and corruption as proof of its vile nature, but I say to you: Look at the predators and plagues of any world - even Ancient Terra - and you'll find things every bit as dangerous.
"Yes, it is dangerous. Dangerous to those who do not have the knowledge or tools to handle it safely."

Or a simpler one:
"MUHAHAHAHAHA! THE POWER!!! IT! IS! MIIIINE!!!!"