When the party arrives they are indeed treated to free drinks and are the heroes of the hour, a few of the waitresses or local girls flirt with them, the bartender chats happily with them thanking them for removing the thug and they have a great time with the promise of half price drinks whenever they are in and perhaps some favours. 

The party begins seeing this as their potential hangout and begin frequenting it more often though only the most astute characters should realise something is a little off about the place at this time I.E: The locals girls with different men each time, a general nervousness around some regulars, the girls vanishing into the backrooms on occasion.

At this point the bartender begins asking them questions along the lines of "If they had heard about those shady deals over in.." in a manner that he is under the assumption the party as local vigilantes already know and intend to do something.
Of course this is all a ploy to subtlety direct the characters towards a rival mob's shipments of drugs and weapons, for the criminal gang at this point everything is a win/win either their rivals suffer a set back or a possible future problem is killed off.

This drip feed of information continues with stories of "My brothers kid in the force says.." and "I've heard from one of the delivery lads.." each with just enough information or a name to have the party start investigating until the group trusts their bartender friend perhaps even coming to rely on him for information more so than other sources even in unrelated cases.

At this stage all these tips have been aimed at obviously illegal operation's that have had no connection to the Criminal Gang but the removal of which would help them stabilise their position in their territory and they can claim they had no hand in the attacks as they were done by a unaffiliated party thus preventing retribution attacks. However a minor complication/opportunity has arisen for the Criminal Gang, one of the corrupt police officers that they pay off so their businesses are ignored is demanding a larger cut. Not wanting to continue paying the corrupt officer nor obviously remove him the Criminal Gang begins a scheme to use the characters group as more direct pawns.

Informing the corrupt officer to collect his pay off from the players frequented bar with the code word "This months insurance" the players observing the transaction. If the party tries to intervene they are rebuffed and threatened by the arrogant and aggressive officer and the bartender pleads with them to not intervene. Once the corrupt officer leaves the Bartender privately breaks down and confides in the players informing them that he caught several of his waitresses prostituting themselves to customers for extra money but rather than throwing them out onto the street where they would continue he allowed them to use the backrooms so they would be safe and not risk been murdered however the police officer found out and has been blackmailing him since keeping all the records in a personal ledger.

The story is a complete lie but the group now face a dilemma, they could report the officer for corruption but their friend would be jailed for allowing prostitution on the premises so now they are increasing forced into the morally grey.

At this point the party may start planning ways to remove the officer whether it would be having him killed, threaten or even framing him for another crime but the Bartender informs them that in order to prevent himself been arrested in the investigation they would have to retrieve or destroy the ledger also. To add weight to this the Criminal Gang after ensuring any illegal goods are relocated elsewhere give an anonymous tipoff which results in a brutal police raid on the Bar a few days later. The players either getting caught up in the raid or seeing its after effects are further enraged and more seeds of distrust regarding the police are sown. Especially as they now believe this raid was a result of the threat made by the corrupted police officer.