Aeros can easily see the slightly charred, unconscious kobolds laying on the floor. Given your previous experiences with unconscious kobolds, you are somewhat wary of them, though you can't hear the high-pitched whine signaling they might be about to explode just yet. 

For everyone: 

You all (except Eryn) are at the top, where the path leads into the door. 

Eryn is to the side where what you can see is a broken table lay; that door is wide open as well, a fallen kobold just outside it. 

Is the fallen kobold outside whining? He should be just a sleep. 

If that kobold is making the whining sound Eryn heard last time, he will seek cover behind the nearest corner that takes him out of danger from the expected blast.

If Eryn can't hear the whining sound coming from the kobold outside, and there are no sounds of fighting coming from within the house, Eryn will quickly relieve the kobold of all obvious weapons and then drag him away from the door. Eryn will then pull his rope from his backpack and bind the kobold so he can't escape. (If necessary, here is a straight d20 roll, without any bonuses applied, for knot tying: 7 DM, add whatever skill bonuses are appropriate.)

Sila looks at the party, "Wh... what's happening here?" she finally asks.

Aeros has a minor coughing fit before replying, "We've been asked by the Watchmaster to investigate a prison escape and our investigation lead us here to the home of a Firemark employee who's somehow involved.  The kobolds here prove that.  Sorry again for dragging you both into this but thanks again for knocking them unconscious.  We should hopefully be able to question them this time."  Then turning to Arthasis & Menodora he asks, "Have either of you seen Eryn?  Maybe we should find him so he can rejoin us for the interrogation?" 

Quote from phillberrie >>

Is the fallen kobold outside whining? He should be just a sleep. 

If that kobold is making the whining sound Eryn heard last time, he will seek cover behind the nearest corner that takes him out of danger from the expected blast.

If Eryn can't hear the whining sound coming from the kobold outside, and there are no sounds of fighting coming from within the house, Eryn will quickly relieve the kobold of all obvious weapons and then drag him away from the door. Eryn will then pull his rope from his backpack and bind the kobold so he can't escape. (If necessary, here is a straight d20 roll, without any bonuses applied, for knot tying: 7 DM, add whatever skill bonuses are appropriate.)

 (My apologies, he is not whining - got myself mixed up there.)

You are easily able to tie up the unconscious kobold. 

Arthasis kept his distance from the dead kobolds, not leaving his position at the door. "I haven't seen him.", he replied to Aeros. "He's a big boy though, he'll find his way." He then turned grudgingly towards the two newcomers, while assessing the damage the bolt had dealt to him. "Thank you for your assistance. It's the second time these creatures caught me off guard."

Listening for the sounds of combat coming from within the house, Eryn will search the sleeping kobold for anything unusual, like a message or anything else it was supposed to deliver.

Can Eryn hear any whining at all?

No whining. 

Roll me investigation for searching the kobold.

Eryn's Investigation check: 12

Any sounds of combat coming from inside the house, or any onlookers?

Sila nods, but enters the house, "If there are escaped prisoners about," she says, "I'd like to help."

Eryn finds nothing on the Kobolds beyond tattered clothing. 

Make a perception check. 

Everyone else: 

A cursory glance of the house reveals signs of a struggle from probably a few weeks past. There's broken furniture, what looks to be an emptied chest with a broken lock, turned over on its side. There's a broken worktable in the corner by the side door strewn with scraps and garbage. 

You may do a closer search of the house if you'd like.

Eryn's Perception check: 21

 Here is a second roll for either the Advantage or Disadvantage: 8

He hears no sounds of combat and doesn't notice any onlookers.

Presuming he can leave the trussed up kobold against the side of the house and expect to be able to come back and find it still there, Eryn will move stealthily towards the side door, weapons at the ready. He is unsure about what is going on, but can't believe there was only one kobold in the house (he has only seen the evidence for one), as far as he knows the little brutes normally move in packs.

Once at the door, he will listen to try to work out what is happening inside.

Stealth roll: 14

Hearing Perception check: 24

Quote from BaconExpert982 >>

Sila nods, but enters the house, "If there are escaped prisoners about," she says, "I'd like to help."

 "I don't mind if you tag along with us but I'm not sure if the Watchmaster would be willing to pay a couple of newcomers to our party.  I guess that's a moot point though if we don't catch this goliath."  Aeros replies before chuckling to himself a bit, instantly regretting it as he winces in pain slightly.  Damn crossbows, he thinks darkly to himself as the pain slowly recedes .  "I guess we should probably tie these two (kobolds) up and then see what clues we can find in here."  he announces to no one in particular.  Walking towards the unconscious creatures, he'll take out some rope to tie them up before inspecting the residence. 

Investigation: 9

Kriv will begin to walk around the house, his shield and mace still at the ready as he investigates. He lightly touches the feather under his cloak "Guide me to what may help us understand."

OOC:

guidance on self

Investigation check: 2 + 4

Though she is equally pained from the Kobold attack, Menodora is going to quietly hum in Elvish and use healing word 6 on Aeros, first. Hopefully to help improve his condition a little. 

Then she'll head over an investigate the toppled chest, to see if there is anything of interest left in it, or around it. 

Investigation: 15

Hearing Aeros' calm voice, Eryn will return to where he left his captive and drag the creature towards the door.

"I caught one trying to escape," he announces loudly as he reaches the open door.

[OOC: At this point, does he see the fourth kobold (the second of the two his Sleep spell affected)? From my reading, the two Sleep spells brought down two kobolds each, so there should be four in the house, including one that Aeros didn't tie up, perhaps because he didn't see it.]

(There are four kobolds in total. Your sleep spell brought down the one outside and one inside. Menodora's sleep spell brought down the other two inside.) 

In inspecting the house, Aeros and Kriv find themselves looking through the refuse around the broken table. Aeros finds a pouch of blasting powder. Kriv finds himself drawn towards a torn piece of parchment: 

Purple flames lick harmlessly at the edges in answer to Kriv's murmured prayer of guidance. 

Menodora's investigation of the chest turns up a pouch with 12 silver pieces spilling out of it. 

If Eryn is going into the house via the side door, he would see the last kobold right as he steps through. 

(Text from the handout above: 

Of all the sources we mine from within the Silberquel, my yield of saltpeter still proves the most pure and powerful! The Firemarks, pry as they might, will have to respect my expertise and contributions to the war effort.

The sheer volume of untapped guano in that cavern behind the top of the falls is invaluable, and once I have enough marked interest from the Firemark Facility, I’ll let them help in harvesting my secret cave.)

Having taken in the scene inside the building, Eryn will first relieve the fourth kobold of its obvious weapons and then secure it back-to-back to the one he brought from outside using the unused coils of his rope. 

Then the tall wiry pallid elf wipes his hands free of kobold grime, removes his smoke-darkened glasses and asks of Arthasis, "Who are these two, and where is Keaton?"