Our intrepid heroes track down Lubor's home through the Underdocks and note a ladder heading up into a trapdoor. The home sits on a bit of a U shaped retaining wall with a single support strut holding it up on one side. As they approach, they see a large rat sit up, sniff the air, and fall over. Captain Archer heads over and takes in a big breath of the air to see what's up and promptly passes out. A series of Heal checks revive him and a series of Knowledge Nature and Craft Alchemy checks determine that there much be a bubble of a gas akin to carbon monoxide that has likely seeped out of the bottom of the house.
Lenny chops down the support strut as the others back away, knocking the house down on one side, then she throws Proteus up onto the docks and leaps up herself. Archer climbs up the side of the wall. Siva and Lhye find a ladder to get up. By the time they do so, Archer has had to frighten a bunch of kids off with tales of poison gas and danger.
Lenny kicks in the door and Proteus sends in the monkey to poke the two bodies spotted lying against the other wall (which is at the bottom of the slope). He ties a rope around himself and gives it to her. He was going to test out the air to see if it's still filled with bad gas by taking big breaths but Lhye (who's the resident medic and Know Nature boy) tells him that carbon monoxide is a silent killer. (Yeah, yeah, in those days they wouldn't refer to it by its molecular structure but we couldn't be bothered giving it an alchemical nickname).
The thickest level was in the bottom-most section of the house (nor one corner / side due to the slant) and with a thinner level that stretched from a table that was bolted down on the sloped floor up to about three feet from the doorway. Proteus slides down the slope and pauses at the table, noticing that there's an open crate from some kind of university (had something stamped on it) that was partially filled with straw. He also notices the drying blood spattered on the floorboards.
Siva has an idea and calls him back up before providing a lantern, Archer provides the oil, and Proteus provides the Spark spell to set it on fire. Then Proteus slides back down and when the lantern's flame burns smaller and weaker, they realise that there's still dangerous gas inside. Proteus plays with the line of carbon monoxide, moving it in and out of the 'bubble' and watching it dip and rise up, then he headed past the table and searched the bodies by hand as the lantern went out.
One man wore canvas trousers with rope bracers and a sackcloth shirt who had a single gold tooth. The other man wore cloth trousers with a cotton shirt who had three gold teeth, a pouch of 100 silver coins (that hadn't been stolen by the killers) and had a receipt from an Absolom Museum in a hidden pocket against his inner thigh. Both men had their throats slit. Both men had their shirts drenched in blood but didn't have very much on their legs from their knees downward. Lhye figured that they'd been executed on their knees and kept from falling.
Proteus also picks up a ripped mottled grey-and-black bag of holding, now punctured by a piece of fallen wood, that has a small symbol sewn on the inside that looks like an assassin's calling card, though they lack the appropriate Knowledges to figure out who.
They head out into the maze of rafts and spot the Hydra's Fang anchored beyond the sea wall. They spot two Consortium officers and their sea cub pet. Lhye stealthily casts Sleep but only the sea cub passes out. Proteus and a Lhye who has used Disguise Self to appear as a Katapesh man approach with alleged snuff (sneezing powder placed inside an Alchemist's Kindness tin) and they are convinced to snort it off the tin. I increased the duration to 1d6+1 rounds because of how it was administered.
While they were sneezing uncontrollably, the group subdued them, stripped them, and Archer and Lenny both put on the uniforms. Lhye used Disguise Self to also appear as a Consortium official. They approached the Hydra's Fang demanding to speak to Du Moire about his debts but are responded to with a hail of arrows. I used the levels 4 - 5 enemies, rather than the 1 - 2 ones, as this party tends to be clever enough to be quite successful. Proteus cut the rudder chains. The group won without any casualties.
Then they spot their own ship sailing out past the sea wall.... Their rudder chains are cut.... There's chum in the water.... And they need to recapture their ship!
By the way, you can find the gas mechanics used in this game over here.