The PCs are contacted in some way (by rich person in an inn? ;-) ) and this is the story which are told for them:
The master, of the one who contacts the PC, has a slight problem. The master is a wizard and he owns a book, called Symbolica, which has some very powerful spells in it (Ie. the wizard in the team might want it himself). But Symbolica is stolen! The master knows who the thief is, another wizard, and where he is. The master cannot pick it up himself because of reasons the PCs won't understand. Therefore he asks the PCs to help him, and he will pay them richly if they fulfil the task. The PCs sets off and do the quest. But it is one thing they overlooked: the truth!
This is the truth: The so-called thief is the rightful owner! The PCs master has fooled them! The master has also set out another team of adventurers who's task is to follow the PCs and make sure they fulfil their task. The second team are told that the PCs is doing this task as a punishment for a crime they have committed. When the PCs finally has discovered the truth they find themselves in a very delicate situation:
No friends, no money, only wounds and enemies. I think they will think it over once or two before they says yes to their next adventure...