While the party is passing through the area, they are abruptly apprehended by an armored man carrying shackles who points a sword in their direction. Close behind him stand two other lightly-armored men with bows. This man is Leonel Janvier, a bounty hunter tasked with bringing a ruthless band of outlaws to justice - and he believes he's finally found the criminal scum he's after!
By sheer coincidence, the outlaws that Leonel is after just happen to fit the exact same description as the party. If the PCs question the bounty hunter's business, he provides a wanted poster, which depicts the outlaws in question, showing that there are exactly as many as the PCs and that each member resembles their counterpart in the party in appearance, tactics, and equipment carried. They have been charged with raiding caravans passing through the region, and there is a high bounty on their heads - 200 gold coins for each member brought dead or alive - which means that Leonel isn't about to let an opportunity like this slip through his fingers.
If the party protests their innocence, Leonel will prove difficult to convince - he will be quick to assume them of using a false identity or spinning an alibi in order to evade justice; in fact, the more the PCs attempt to make a case for themselves, the more convinced Leonel will be that they are the exact sort of disreputable ruffians who would make such excuses even in the face of inscrutable proof. In effect, he's already made up his mind that the party is guilty, and only clear, indisputable evidence will change his mind - for instance, if the PCs can prove that they were somewhere else at the time of the latest caravan attack (it happened about a week ago), he'll let them go. On the other hand, the upside of Leonel's tendency to judge others is that he has a very black-and-white view of the world, and is quick to make assumptions of one's guilt or innocence based on how consistent he finds it with their character - so, if the PCs can provide proof of them doing a great deed of heroism in the past, he will find it so difficult to reconcile with the notion of them being outlaws that he will assume they can't possibly be the people he's after. After all, an outlaw could never be so honorable!
Perhaps fortunately for the PCs, Leonel will try to bring them back alive if it all possible. If he is able to restrain them, or if they agree to come with him voluntarily, he will lead them to the nearest town (or to the nearest guardhouse or lock-up if already in a town) to hold them until trial can be held. However, he isn't afraid to fight if he must - and if he feels threatened for his life and the PCs show no likelihood of yielding, he won't hesitate to use lethal force. If encountered in a town, and if a fight seems inevitable, he will request to move to somewhere where there will be little risk of the battle endangering any civilians, such as outside the town walls or to an alley that sees little traffic, if possible.
Should combat occur, Leonel has the stats of a knight. He also has two deputies (stats as scouts) at his back who will join in any combat that arises. Leonel won't hesitate to fight to the death if he must, but if he is killed, the PCs might end up with an actual bounty on their heads if his body is discovered. His deputies are more reluctant; if Leonel dies, both deputies must make morale saves (see here), or flee combat. If one deputy dies, the other must also make a morale save, though Leonel himself will be undeterred, thinking he can handle it.
On the other hand, if the PCs can prove their innocence to Leonel, he may request their help in apprehending the brigands. But why is it they seem so similar to the party? Is it a simple coincidence, or are they being framed by impostors or dopplegangers?