Bounty Hunter
You are relaxing in the Bucket and Broom tavern when the door bursts open and a barbarian rushes in, looks around frantically and demands to know if you have seen a "greenskin" running through here a moment ago. He waves a poster that has a roughly-drawn picture of a half-orc above the inscription
WANTED for MURDER
Gruzhnag aka Off-Ears
1000gp reward, dead or alive
When it becomes apparent that the fugitive has given him the slip, the barbarian calms down and, in exchange for a mug of ale, is willing to elaborate.
He introduces himself as Tonso and he is a bounty hunter. His quarry is accused of the murder of a rich but unpopular merchant called Lorenzo di Barborro. A lot of people owed Lorenzo money but under the local laws, now that he is dead, they won't have to pay it back so there is not a great deal of sorrow over his death. The di Barborro family is quite unhappy however, not so much that Lorenzo is dead but that they as a family stand to lose a lot of his money. They have offered the reward hoping that the killer can be caught and tortured to reveal which of Lorenzo's many creditors hired him.
Tonso knows the whereabouts of a mini-dungeon where Gruzhnag is thought to hide out. If the PCs care to accompany him as back up he will lead them there and, if they capture Gruzhnag he will cut them in for 5% of the reward (negotiable).
Stat Tonso as a human male barbarian of the same level as the average party level, optionally with the Urban Bounty Hunter background from SCAG.
If cornered, Gruzhnag will turn out to be a snivelling coward who will try to trick his way out of trouble. He didn't commit the murder but he knows who did. A syndicate of Lorenzo's creditors hired the assassins guild to do the crime, having lured Gruzhnag to the scene beforehand with the intention of falsely incriminating him. He doesn't expect anyone to believe he is innocent, however, which is why he fled. In return for his freedom, he is willing to lead the PCs to the headquarters of the assassins guild, near the docks. Tonso, however, is unwilling to forego the 1000gp reward.