Galia goes undercover posing as Octavia Khan. Her and the newly arrived Psyker, Name? and Tech Priest Name2? go to a shadier area of the merchants quarters on Port Gavinus Station.
Following the instructions for the meetup Galia and Name? enter the Pawn shop, give the code of "I'm looking for Hallister" and enter a back room. They are met by three people bearing weapons. After giving the pass phrase of "I'm from Tongetta IV in the lower province." they lower the weapons, but notably fail to holster them.
Galia (as Octavia Khan) provides the leader, Calamity Keller (a black market/fence) with the goods in a chest. The gorup was provided with imitation vials to replace the ones that broke on the trade ship and imitations of the ones still intact. Following the transaction (which netted them a good number of Thrones), the group sets up a stakeout on the pawnshop.
Soon a group of people in ganger colors show up and enter the shop leaving a few outside to stand guard. The group hears weapons fire shortly after and the gangers leave carrying the box that Galia turned over.
The group begins trailing them. The station security guard, Tarkus who joined with the group says that it looks like one of the gangs from the Lower Warrens.
The group does follow them to the Lower Warrens, which is a delapidated and worn out area of the station. Many of the areas are darkened and uninhabited. The group follows at a distance and finally comes to what appears to be a guard station for the Mongrel's territory.
The psyker uses his abilities to stealth toward the guards as the assassin sneaks up. This does not work and combat ensues. The acolytes make short work of the gangers.
Passing on they find an area that is isolated, but functioning as a small village inhabited by the gang. It is easy to stick to the shadows and soon they see a group coming their way. The group appears to be at least one of the ganger leaders, a couple of men who don't quite fit in and several of the regular gang.
They shadow this group into a maintenance corridor that leads to a huge room. The techpriest identifies it as the air recyclers for Port Gavinus Station. He explains that the stations air supply is pulled in here, scrubbed and fed back out to the rest of the station.
The group watches while the group approaches what appears to be a pentagram drawn on the floor deeper into the room. Two techpriests stand at the side and operate what appear to be controls for the room.
The acolytes attack before the ritual can be completed and a gun battle starts up. While the rest engage in the fight, Name? uses his powers to climb the walls and cling to the ceiling. He goes overtop the group and watches as the leader pulls the fake vials out of the chest and several other vials that they must have obtained earlier. Name2? tries to access a panel where he may override the controls to the air filtration system.
With very little ritual, the cult/gang leader begins chucking the vials on the ground where they either are useless (the fakes) or begin bubbling up either Plague Bearers, other creatures or in one – a mass that absorbs the other daemons and grows with each creature it touches.
This final mass is mutating and great tumors grow and burst from it as they watch. Each burst tumor flings a gas into the air. Nearby gangers are immediately stricken and drop where they stand dying a horrific and quick death at the daemonic disease. Their bodies become part of the unholy mass and the gasses continue to build and move toward the air blowers leading the rest of the station.
The techpriest finally overrides the controls and stops the air from leaving the room. Meanwhile, the fight, which was bloody, but indecisive is put on hold as all combatants remaining realize they are doomed if they stay in the room.
Rushing out f the room, they are met by Interrogator Thorne who they have maintained contact with throughout. Thorne is accompained by a squad of Grey Knights who have arrived on the Inquisitors ship. The Grey Knights enter the room and quickly cleanse it in holy flame.
The threat to the station and the evil is stopped. Had the group failed to stop the air filtration – potentially thousands would have perished at the hands of Chaos.