Meili flies down and approaches the open door to the interior of the guardhouse.  She sees that it opens into a long, narrow hallway that appears to run all the way to the far side of the building, ending at a closed door.  Predictably, there is no sign of Mica.

Mica frowns as he looks into the room, the building is much bigger than he thought from looking at it from the outside.  Murderholes and arrow slits along the hallway will make this tough to clear. Two more inner doors leading to who knows where, with who knows how many guards?  With nothing else to see, he makes his way carefully back down the hallway toward the outside. Maybe he could find Meili and figure out something to do about the guards on top of the building.

[A sketch to make the descriptions (hopefully) a little clearer.]

Obviously, she could not see Mica inside the hallway, he was invisible after all.

Meili dared not call out, and it was too late to regret not agreeing on some signal beforehand, like a familiar scent to mark each other’s presence. But she still had one option.

Stepping into the hallway, she deliberately pressed one foot into the muck on the floor, leaving a clear impression to announce her presence. Then, keeping her arms outstretched to touch the walls, if they were within reach, she moved slowly toward the closed door at the far end. Sooner or later, she was bound to find him.

Perception to see Meili's footprint : 20.  Passive Perception: 15.

Mica notices a muddy print appear, as if from no where.  

[It is safe to assume Meili has joined him in the hall.

Meili, meanwhile, still can't see Mica or even know for certain if he is still in here.]

Then - bump - the invisible arm of Meili makes contact with the invisible chest of Mica.

Once Meili’s outstretched arm brushed against something solid - Mica’s chest - she tapped it lightly a couple of times to confirm it wasn’t a mistake, then barely audibly whispered, "Did you try to open the door?"

If Mica agreed, she would carefully take the handle and attempt to open it herself, moving as silently as possible.

Even after seeing the footprint appear in the mud, Mica jumps when he feels Meili touch him. “Bloody hell!  You scared me half to death” he whispers back as he hears her voice. “I didn’t try the door, there are three others in the room, you can see them through the murderholes in the hallway.  Another door from that room leads deeper in the building.  What did you find up top?”

Meili chuckled softly. "Two guards and a hatch - probably - covered with leaves," whispered she in return.

She looked in the murder holes in the walls, peering at the guards on the other side. "Let's see if this door is locked. Maybe we can figure out how to block the inner one from here."

Without further hesitation, she went to the door at the end of the corridor and tested it carefully.

Meili tries the door carefully.  It is unlocked but stuck.  She is able to carefully get it open and it reveals another long hallway running along the exterior wall of the building.  There is another door at the far end, along with a near door which would open into the room with the guards.  

"HOLD!"

Mica and Meili both have to stifle gasps when a voice cries out, but they quickly realize it is one of the guards on the rooftop shouting, not anyone inside.

Outside, Ran, Danica, Nalomanterys and Eligos see a faint light appear out of the rain.  It looks to be a torch or lantern, wielded by someone walking down the path from the jungle above, down into the ruined city.  As it draws nearer, a guard on the rooftop cries out "HOLD!" training his crossbow on the light.  The light hesitates, too far to get a clear look at who is holding it.

 [You forgot to place that new door on the map)

Meili froze at the sudden shout, but quickly realized the voice came from outside. Someone was approaching through the storm - was it Ran's decoy or some coincidence? Either way, the guards were focused elsewhere for now.

She leaned closer to where she guessed Mica was. "Distraction," she whispered barely audible. "The guards can run out to call, let's get past that door to the room."

Without waiting for a reply, she started toward the inner door at the end of the next corridor, staying as silent as the falling rain.

Ran draws his own crossbow out and trains it on the guard aiming a crossbow on the light bearer. He's guessing the one holding the light is probably as bad news as the guards but just in case it's someone that might be useful, might be best if they didn't let whoever it is get killed. He holds his shot for now.

Ran, make a Perception (w/disadvantage due to the storm) check, DC 12, please.

Ran Perception: 6 

Mica flinches and looks back toward the door to the outside when he hears the shout. He also doesn’t want to be in between the guards inside and whatever is coming from the outside.  “Right behind you”  Still, he is curious to what caused the ruckus and as they reach the end of the hallway he whispers “Shouldn’t we go see what it is, it could be Ran or the others?”

Mica and Meili both slip inside the door and move quietly down towards the far end of the hall.  After they pass, the door to the guards room opens and one of them, crossbow in hand, steps out behind them.  He looks back over his shoulder and into the room.  "Hold tight, but get your gear.  I'll check it out.  If its trouble, be ready."  Then he takes the safety off his weapon and moves into the other hall, toward the outer exit.

Outside, Ran can't see anything more than a light bobbing in the rain.   Around Ran and the others, lurking at the edge of the ruins, it is dark, wet, and quiet but for the falling rain.

[If anyone wants to do anything in this moment, let me know.  Otherwise I will move onto the next event...]

Mica holds tight in the hallway and watches as the guard heads out to investigate.

For the moment Meili follows the plan and gets to the inner door to listen to what is on the other side. If all is quiet, she would try to open it.

Ran targets the bobbing light with his crossbow but hold off on firing for now.

Meili creeps down to the end of the hallway and checks the door there.  There is no sound.  It is unlocked and she is able to open it slowly.  It opens into a dark, windowless room.  From somewhere inside, rainwater is dripping in.  The room is full of simple wooden cots.  A shape lies sleeping here... one more guard, it looks like.  They do not stir or notice her at the door, for now.

Mica watches as the guard with the crossbow rounds the corner and heads out to the front door to the structure. There is sound of movement from the larger room as the remaining guards prepare themselves.

Outside, the storm rages on, rain pelting the ancient stones of Omu.  Ran, Danica, Nalomanterys, and Eligos crouch silently, their soaked cloaks clinging to them as they peer through the downpour at the old guardhouse.

A single guard emerges cautiously from the same door.   His crossbow is ready, and he scans the scene with a practiced eye.  A subtle nod is exchanged with the two mercenaries stationed on the roof.  There is still no sign of Mica or Meili.

Through the sheets of rain, the lantern’s light flickers unevenly, giving the impression it is moving again.   Then a shape begins to materialize in the rain.  As the man staggers closer, his features come into view—drenched hair hanging beneath a helm, the breastplate of the Cormyr Company mercenaries glinting faintly in the storm’s sporadic flashes of lightning.  His movements are unnatural, each step uncertain, as if he is on the verge of collapse.

The figure falters, setting the lantern down beside him.  Its glow casts distorted shadows on the ground as he sways, then falls heavily to his knees.  A moment later, he crumples completely, collapsing face-first into the muddy path.

"It's the lost patrol!" one of the guards on the roof shouts, his voice sharp with alarm.  "There's trouble!"  The other nods.

The guard on the ground hesitates only briefly before shouting back over his shoulder inside the guardhouse.  His words are lost to the storm, but his urgency is clear.  Then he begins to move, crossbow raised and eyes darting left and right.  His boots splash through the growing puddles as he advances toward the fallen figure.

The storm swallows him as he crosses the distance, his form growing less defined until he reaches the motionless figure.  For a moment, all is still save for the pounding rain.  Then, in an instant, the lantern’s light snuffs out, plunging the scene into darkness.  Both the fallen mercenary and the guard vanish from sight in the heavy rain.

The silence that follows is deafening, broken only by the relentless drumming of rain on stone and the occasional roll of thunder. From the rooftop, one of the guards curses loudly, his voice trembling.  The next flash of lightning offers a heartbeat of illumination - there is no hint of either guard where they had just been moments ago.  "Mykel! MYKEL!" shouts one of the guards on the roof.  His desperation echoes through the rain, unanswered.

The guards exchange a terrified glance, their earlier composure cracking under the weight of the inexplicable.  The guards on the roof nervously scan the shadows, their crossbows trembling in their hands.

Back inside, Mica and Meili hear a voice shout in from just outside the front door.  "It's the patrol!  I think we'll have wounded.  I'm going out to have a look.  Heat up some water!"

After a pause, the sound of movement in the larger room intensifies.