Back at the office, Colin decides to find Costello's rat once and for all by putting surveillance on Captain Queenan and waiting for Queenan to lead him to the rat.
Queenan eventually takes the people to the subway, where Billy calls him and asks him if there's someone tailing him. Queenan assures him there isn't, so Billy leads him to an address.
The guy tailing Queenan reports back to Colin that Queenan is meeting the rat.
So Colin goes ahead and calls Costello to tell him the address where the rat is meeting Queenan.
Back on the rooftop of a building, Queenan tells Billy that he's going to start the process of pulling him out of his undercover job.
While meeting Queenan, Billy gets a call from Delahunt saying that the gang is about to go kill the rat, who is apparently meeting with Queenan on Washington Street. But Delahunt gives him the wrong address, saying 314 instead of 344. Billy hangs up and tells Queenan that they have to get out of the building immediately.
But it's too late. Costello's guys are already there. Queenan stays to create a diversion while Billy takes the fire escape out of the building.
Billy tries to walk away from the building, but Queenan lands and dies right in front of him: Costello's men chucked him out a window.
Meanwhile, the cops following Queenan want to know what the heck just happened. Colin tells the cops not to engage Costello's men, but the cops disobey and get into a shootout. One of them shoots Delahunt right through the gut.