Such as?
There are no alarms going off.
((Alexei will grab his healing ring and put it on, supress the parma a moment and turn on the pain reducing affect. All of the Soak buffs are still active, so he'll pop the spear head on and head out of his sanctum. He's not going to cause a panic yet, he's going to go the captain of the guards for this shift and get a report on any activity; visitors, sightings, anything out of the ordinary and tell him to get him a turb of grogs, 5 of them and meet outside Alexei's sanctum, and send a note to the Imperator (it will be funny of he says "That's you sir") to come immediately as well. The alarm will be raised if he sees anything out of the ordinary))
((This might be spreading Marko a bit thin... It's up to him. We'll just say that Alexei has the guard doubled, and sends a note to Roberto as to why.))
While Alexei is discussing things with the captain of the watch, everyone returns from Val Negra without incident. Twenty-four hours pass by, with nothing happening...
Alexei is going to spend just a bit of time questioning the ones that have returned from Harco. Just Helmut, Michel and Brionne would be fine, questioning Isen more than a simple report on what happened at Harco might be inappropriate. Once he finds out that everything went fine coming from Harco as I assume it did, he'll simply ask them about the incident with the bandit kidnappers from years ago, Alexei is not yet aware that two have spoken to Fiona about it and assumes it's a bit of knowledge that is a secret the four of them have. If they all give a similar recollection of the event, Alexei will assume that they haven't been replaced by doubles. The key bit of knowledge that might trip up an impostor is that Helmut believes Alexei was drunk, while Brionne and Michel know that he wasn't at the time.
Once that's done he'll advise Jacques and Roberto to please keep an extra watch with the grogs and that someone has impersonated the Prima in a letter and sent him on a wild goose chase.
So I don't assume too much, the initial messages were sent by a Redcap? What was the Redcap's name? There was the initial letter Alexei and Isen received, and then Alexei sent a message asking about the passage to Harco. Did Ariel send a message back? It could also be that the Redcap (if he knew) would have just informed Alexei that there is a passage to Val Negra that he can use. Based on this info will determine my next actions, but one thing will likely be to call a meeting first of the Flambeau at Mons Electi. This could be either a House issue, or a Covenant, or simply directed at Alexei and I don't want to over react and involve the others yet.
Bandit kidnappers? The ones who took Mufarjj?
As far as the letter, it depends on how perceptive Alexei is, would it have been reasonable for it to go to a page, first, and be brought to Alexei? Redcaps come through here fairly regularly with the Portal, so there is a reasonable possibility that Redcaps are background and blase by this time. Or at least, if one is in a hurry and says this is for Alexei, and that he has other errands to run, a page isn't going to think twice and stop and ask him who and what his name is...
As far as sending the letter back and forth to Ariel, same thing...mail is sent to Harco almost daily, gets sorted and sent off to its next/final destination.... Maybe getting a Redcap involved in the story could help... 
No, sorry, there is a part of the story in 1227's events where Helmut and Brionne talk to Fiona about an event with bandits before Alexei came to Mons Electi, bandits kidnapped Fiona and Alexei killed them with extreme prejudice:
Is there a Redcap that resides at Mons Electi? I don't mean Korvin, who is a Gifted Mercere, if Alexei can't think of Redcap he'd ask Korvin of any Redcaps that regularly visit or stay at Mons Electi, if he can't he'll ask Korvin ((I honestly am not sure of the names of any Redcaps at the Covenant)), but he'll also try to get the pages to recall who gave them the message.
Reynaud. 
((There we go! I knew it.))
Alexei sends a page for Reynaud, hoping that he's still at Mons Electi and not on duty.
On duty? Him? That's rich!
That is Renaud. He can be found in the Covenant's tap house/mess hall working on a song on his lute.
Alexei heads straightaway to the tavern with Michel and Brionne in tow. Once there he looks about the tavern, squinting in the poor light. Finally giving up he announces to those in attendance:
"Renaud? Is Renaud here? I need to speak with him quickly."
((Alexei is not likely a stranger to the tavern scene, the way he interacts with the men and his Gentle gift, but coming in here all business will likely seem odd))
Saw Roberto's name mentioned. What do you need of him? I have no problem multitasking, but I will be unavailable until Sunday night.
Once Alexei gets a few answers he'll be calling the Flambeau together. Knowing Roberto's feelings for Ariel he might not care too much, but I'd mainly like him (as Imperator) to keep the grogs on high alert for whatever is happening. I was expecting an attack on Mons Electi already as soon as Alexei left.
((Sorry. Lost this thread for a bit))
The room quiets down and some men look to a back table. A bearded man, dressed in various shades of red, is leaning back in a chair with a lute in his hands. He plays some more cords to himself before he answers in a slow and lazy tone. And who would be looking for Renaud?
Alexei turns and nods to the grogs, who nod in return...and then head to bar and get some drinks. Alexei approaches Renaud, pulling a scroll case out, leveling a very serious stare at him as tavern folk step aside. Once there he leans a bit on his spear (not a staff) and takes a chair and sits across from him.
"I..." he begins but Brionne has returned with a tray of drinks and interposes between them. "Thank you Brionne." Alexei takes one and the other is offered to Renaud. "I would like to ask you some questions about these letters, and who delivered them. Can you do that for me please?"
Renaud looks at Alexei for a moment then down at the letters. After a long time ( for Alexei) he slowly puts all four legs of the chair back on the ground. He talks a slow pull on a beer and puts the mug down. I'm not sure what mystical qualities you imbue upon my brethren to know all of the various and multifarious goings on of the Order nor of ones such as Renaud to ascertain enlightenment from hither-to unknown communiqué. But as you are a friend and compatriot of Korvin, Renaud will strive to entertain and enthrall you as to these phenomenon.
Alexei hands over the letters to Renaud. "Merci beaucoup." and takes a drink. There's a brief commotion at the door as the huge mastif pushes his way through, nose to the ground, unconcerned about who he bumps into as he unnerrignly heads to Alexei, but not without taking a scrap or two from some tables. Once at Alexei's side he drops a heavy paw on his lap and looks directly into Alexei's eyes. The dog looks remarkably like another dog that has been seen around the covenant since fall, except he's smaller. The other dog is as big if not bigger than warhorse, while this dog is quite large it is still of a normal size for a dog.
The magus seems to get defensive as the huge dog puffs out his chest and begins to make low growls and barks. Alexei responds to the dog in annoyed tone. "I wasn't gone for long! Barely a few hours! No, I told you that it would be brief and that Fiona would come to visit. Look, can we do this later? Fine! I'll get a mutton leg for you!" The dog seems to nod his head and then looks at Renaud briefly before taking Alexei's drink in his mouth right off the table and bringing it to the floor where he begins lapping up the ale right out of the mug. "I was drinking that! Nevermind." Alexei can finally return to Renaud.
"I'm sorry, this is Donner, he is very possesive of my time. Renaud, that letter was delivered by Redcap to a page who gave it to me. I know Redaps come and go at Mons Electi with some frequency, perhaps even you were the one who delivered it. But the letter is false, it claims to be sent by Ariel, the Prima of Flambeau, as well as the second response. But she never sent it. It wasted both our time and also could have been part of ruse to set an attack or ambush. Can you tell me or find out which Redcap delivered the messages so I can speak with him?"
This presumes he survived his adventure last year and was not horribly transfigured by it
Ariel is my Prima, and I am ever ready when duty calls. But I fear you may be right, this was a trick on us. And the target may be the two of you, or others of your societas. Check in with them, see who else has recieves messages to go there or anywhere. And keep me posted and call on me as needed. Have Cidito share his scent mark with you, I will have him check in on you, and if you need me, send him back along with an Arcane Connection for me to use and I will magically transport myself to your side.
Isen was not happy to see this trick played on them. So? He frowned, of course!
Now...
The letters. Hopefully, they should still be arcane connections to whoever wrote them. This can help us.
Renaud regards the letters for a moment then leans back in his chair and picks up his lute and resumes his former position.