Shipwrecked in Saltmarsh

Molo yells at Seth “Watch where you’re swinging that, you jerk!” 

Then he picks up the scimitar, dagger, and crossbow/as many bolts as he can

Katernin lifts up the papers to read them. When the guards start to argue she goes to intervene. "What's the issue here?"

Katernin begins to examine the notes. Investigation: 12

It's a signaling system of some sort, which utilizes a lantern to communicate messages (between a ship and shore, perhaps) by combining long and short flashes:

Long–short–short–short: “Is it safe?” 
Short–long–short–long:  ...

...She is interrupted by the arguing guards. Seth is clearly very angry with his men.

Red-faced with semi-stifled fury, Seth kicks violently at the "Danger" door a couple of times, before realizing that the door opens inward.

The dark chamber beyond is only about twelve feet deep, and the corners are filled with shadow. What little you can see is dingy and dirty.

(Sorry, couldn't post over the weekend)

Quickly, before the guards open the barred door,  Dain will have a quick check around the southwestern corner of the room in case he spots something others missed.

Investigation: 12

He will then move to the front of the party, but behind the guards, ready to face whatever is behind the barred door.

Dain examines the shelves next, and notices something Fianna and Molo did not: some of the shelves slide away; there seems to be a camouflaged door or panel behind them.

But before he can investigate further, Seth opens the barred door; Dain sprints over behind Seth. Butter sits up with difficulty to watch. 

But then Seth steps back and closes it again. "Just bones," he says. He looks a little sobered and pale after peering into the pitch-dark room.

"Really?" asks Dain, stepping past the guard.  Hefting his frilly maul he opens the door and stands in the doorway, letting his Darkvision pick out more in the room than perhaps the human could.

     “Doesn’t make much sense to mark an empty room ‘Danger.’ Even less when it appears the door has been tried from the other side,” Fianna says.  She too sticks her head in to see what can or cannot be seen, being sure to check the ceiling and peer into the corners...

Katernin takes the papers with her later to read, and follows Fianna, "Be careful," she says.

With that, six skeletons slowly rise from the debris on the filthy, darkened floor. They are coated with a thick, dried, yellow substance that flakes off in places as they begin to move. They carry ancient-looking shortswords and shortbows, and are clearly advancing upon their intruders with hostile intent.

Initiative:
Fianna: 3
Katernin: 0
Kelnan: 19
Molo: 9
Dain: 18
Seth and Farley: 4
Butter: 2
Skeletons: 4 

 Kelnan and Dain may act first. (Kelnan is 30 feet from the doorway. Dain is within five feet of one of the yellowed skeletons.)

"Look out!    Filthly undead beasties!"  Dain tries to clobber the nearest skeleton with his hefty, and slightly frilly, maul.

Attack: 7 Damage: 12 (bludgeoning damage, in case it matters)

He swings wildly, though somewhat put off by the idea of moving dead bodies.  He does try to put himself between as many of them and Fianna as possible.   For now he's keeping his rage intact, but it's bubbling away under the surface...

Kelnan scrambles over toward the doorway, trying to catch a glimpse of what lies beyond, and snaps at the guards.

"Maybe we don't just wander into the danger room! Remember the traps?" 

Really though, an animated skeleton? Something interesting at last!  I just hope that dwarf doesn't go get himself killed as well. 

He tries to get an angle to fire a Ray of Frost at the skeleton visible at the south end of the room.

Attack: 13 Cold Damage: 2

Kelnan hustles himself over behind Seth and fires a beam of light into the dark room. It misses the skeleton, leaving a spot of frost on the far wall.

Dain misses completely, smashing a divot in the wall to the south.

Farley rushes over and fires a bolt into the room.
Heavy Crossbow attack:  15. Piercing Damage: 5

Seth shoves Fianna aside and attacks Skeleton #2 with his longsword and some fancy footwork:
Longsword attack:  20. Piercing Damage: 5

(Slashing damage, actually; crit roll +6 damage) 
Bones fly as Seth rams his sword nearly entirely through the skeleton's ribcage. It still stands, badly smashed.

Skeleton #1 attacks Dain:
Shortsword attack: 19. Piercing damage: 7

 Dain easily parries the undead's blade.

Skeletons #2, 3, and 4 converge around Seth:
Shortsword attack: 14. Piercing damage: 5
Shortsword attack: 10. Piercing damage: 5
Shortsword attack: 7. Piercing damage: 4

 Seth goes down hard in a flurry of rusty blades.

Skeletons #5 and #6 fire their bows at Seth:
Shortbow attack: 6. Piercing damage: 3
Shortbow attack: 20. Piercing damage: 4

 The skeletons sink two more arrows clear through Seth's plumed helmet and deep into his brain. He will not be getting up again.

Katernin and Molo may act next.

Molo runs up to the doorway and lays down a phat rhythm on his dulcimer, casting bane on skellies 2,3,4 Cha save DC 13

Skeletons #2, 3, and 4 fight off Molo's bane with their feeble undead willpower. Charisma saves: 16, 13, and 16.

 Rather unexpectedly, the bony monsters manage to fend off Molo's destructively phat beat.

Katernin may act next (and Fianna may queue up her action as well.)

     Fianna will sue up her Eldritch Blast and target Skelly 1.  If by any chance #1 is down by Fianna's turn then #3 will be targeted.  Fianna will then step outside of this room to get out of the bonus line of sight and allow the more front line bashers to get inside...

Eldritch Blast Attack: 13 Damage: 5

Katernin seems even more frustrated and sad as Seth falls before she can even try to help. Pushing her way into the room, she raises her handaxe and swings it down on one of the skeleton trio.

Action: Handaxe Attack on SK3
Attack: 7 Damage: 7

Katernin swings her handaxe at Skeleton #3, but her weapon fails to connect with the surprisingly nimble skeleton.

Still sitting on the bunk, Butter fires a wild crossbow bolt past Kelnan and Dain at skeleton #1:
Crossbow attack: 11. Damage: 4

In another improbable shot, Butter manages to hit it square in the skull, knocking it clean off. Skeleton #1 crumbles into a pile of inanimate yellowed bones.

Fianna fires a crackling beam of unworldly color at skeleton #3, searing it significantly. It is barely holding together. She retreats from the room.

Kelnan and Dain (if Blakey's still here) may act next. 

Moving forward with purpose, Dain Ironforge hefts his improbably frilly maul and growls at the undead before him.  He steps across the prostrate form of Seth the guardsman and stares the three advanced skeletons in the face.  "Is that all yer got?   Well?  Is it?" he snarls.   Swinging his maul at the middle one (#4) he tries to cave it into little pieces.  Finally he lets the pent up anger out, putting everything he has into the swing!

Bonus Action:   Rage (2nd use of 2 today)
Move:   Push into the middle of the room
Action:   Recklessly swing with maul on SK4:  Attack: 24 Bludgeoning Damage: 15

(Note this means Dain is attacked with Advantage for the rest of this round (Reckless), but takes half damage due to Rage.)

In an angry, frothing frenzy, Dain clobbers skeleton #4 in a wide, wild swing. The clavicle and a few ribs fly off, and flakes of the yellowed coating fall away. It still stands; its arm barely hanging on. The skeletons clack their vacant jaws in unison at the crazed dwarf.

Kelnan may act next.

Kelnan steps into the room, looking nervously at the pile of bones he doesn't entirely trust to stay collapsed, pulls a liquid blob from the air, and lobs an Acid Splash at skeletons 4 and 3. "Look out, chemicals incoming!"

2 acid damage, DC13 Dex save to avoid.