((If someone wants to go after Marcus, form a brute squad. Fiona can then show everyone how to get to the Blacksmith, and even come along and embiggen the party, if that's their desire.))
Theraphosa is.....interested? Not sure if that's a wise idea.
Korvin would love to help and should go along to heal anyone but he is far from being a brute squad person.
Tranquillina could come along in a scouting role (and is happy to do so), although she's not too useful in a fight.
Either way: [color=magenta]"Does anyone have an Arcane Connection to Marcus?" she queries. [color=magenta]"I could use it to see him, possibly, and hear what is happening near him."
Fiona thinks for a moment. [color=blue]"I don't believe so, no." ((OOC: I don't remember anything of Marcus's that we could use as an AC to him.))
Listen for rumors of dead sheep and maybe find his familiar?
We should search the covenant archives in case he wrote a letter, signed something, etc. Tranquillina can also go just outside his sanctum and sweep for hairs, etc.: what's the correct Base Level for an InCo spell to detect the presence of body bits? Or maybe she can do it the old-fashioned way, with Eyes of the Eagle and a good light.
Marcus isn't a member. He's just like this guy, you know?[1] We met him at the Tribunal. We've killed some vampires with him before. We have his number, in case $h!t needs to burn. It is not entirely clear if he's ever slept in the covenant.
[1]Massive geek points if you get the reference.
Hasn't he been a Protected Guest of the covenant since the Tribunal, about a year ago? He might have been staying in the manor on the regio side. And, since I don't think he took his fire drake with him, it should be easy to track the familiar down. Just follow the smell of smoke.
If not, and assuming he doesn't have a sanctum marker on where he's been staying, we should be able to find something. Clothes, hairbrush, something we can use for an AC.
Decide who's doing what and then proceed. I'll kick off a new chapter and award XP here after that.
Isen will go.
After his discussion with Fiona, he is eager (so to speak) to meet the blacksmith, so he might as well kill 2 birds with one stone.
Unfortunately, using a fire drake as an Arcane Connection might be frowned upon, by the drake....
Okay, time to bring out the big guns here (or at least pretend to be a big gun). Tranquillina will go to the covenant's ceremonial casting room and spend five minutes sponting (hopefully) the spell Sight of the Molting Magus from HoH:TL, page 72: it causes Corpus material to glow red to her vision. She'll use exaggerated words and loud gestures (or the other way around). Here we go: Sta -3 + In 6 + Co 27 + aura 5 + words/gestures 2 + casting room 5 + Talisman attunement (eyes) 6 + Artes Liberales 1 + stress die 3 = 52 / 2 = 26 - made it.
She'll then go to wherever Marcus was staying and start looking around for hairs, fingernails, stray bits of poo, whatever. Oh hell, walking means a Concentration roll, which is based on Sta, not Int. 
Well ... Sta -3 + Concentration 1 + stress die 5 = 3, just barely. (The juxtaposition of how hard the last two rolls are for Tranquillina really says a lot about her, eh?) Even if there's a sanctum marker, she'll ... gulp ... go on in (after calling his name a few times, just in case) - but not to the point of crossing any Circle-looking wardy things (not that that seems likely).
Assuming she finds something, she'll gather up whatever she finds and go back to the casting room, to double-check that it's from Marcus - that's The Whole from the Part from the same HoH:TL page. She doesn't need to scream this time: she gets Sta -3 + In 6 + Co 27 + aura 5 + casting room 5 + Talisman attunement (Corpus) 3 + Artes Liberales 1 + stress die 2 = 46 / 2 = 23.
Hopefully this results in a verified Arcane Connection to Marcus; if so, she'll have other ideas for how to use it before they depart. Either way she'll report back to the others, and she's kind of tempted to accompany them.
As a familiar, the Fire Drake has an Int score and all the languages that Marcus knew when he bound it. This presumably includes Latin. The PeneAid from the Familiar (+4) is way higher than from that bit of skin and hair(+1) you found.
a) It's a spont, so make it Diameter instead of Concentration. Then you can Leap to the door of Marcus's room.
b) It's a 5th-magnitude spell, meaning it takes 15 minutes * 5 = 75 minutes to do it, not 5.
c) If we're willing to wait a day, and the Fire Drake was willing to provide us with his birth details, then one person could do his nativity horoscope and another person could do his daily horoscope, while whoever is casting the spell can spend it building a symbolic representation of him -- +5 to the multiplier.
d) If the Fire Drake really trusts us, then he might also be able to provide any Names that Marcus has we don't know about, for another +2, bringing us up to a x12 multiplier.
Alexei and Fiona have the highest Penetration, 3. Alexei's Penetration specialty is Corpus, which would get us to a base Penetration of 48.
"Now. Who has Wizard's Communion memorized by now?" asks Viscaria, seizing upon Traquillina's Initiative.
Hmm, reasoning with it. Never thought of that.... If someone wants to go find it...!
A better idea in hindsight. 
Aha! HoH:S, pages 59-60, tell us that "prepared spaces" for ceremonial casting reduce the time as well. I'm pretty sure Mons Electi's room qualifies as the "one minute per magnitude" variety at the end. That makes the room worth it even if there were no Casting Total bonus!
I think that the horoscopes also have to be done by the person casting the spell. I know it's more explicit for the symbolic representation (ArM5 page 84), but it does say "Caster" for the horoscopes. Unless it means "caster of the horoscope"? But "Caster" is used in the blood relative line and clearly means "caster of the spell" there too.
Tranquillina reluctantly raises her hand in response.
Korvin raises his hand.
[color=blue]"Who among us has the best chance of surviving a fire-drake hunt?" Fiona asks with a smile.
As does Fiona.
"Well, I've met him before. On that island with the vampires. I can go looking for him."
We've got a problem. IIRC, arcane connections fade when crossing over the magic realm. Of course, our characters don't know that yet 
Isen frowns
Not yet, sadly. (He learns it in 1225)
(BTW, WTF?? Someone changed some of the background colors for some seasons of Isen in the Magi Planner - Why? - And I can't change it back)
I'd bet on Alexei, with me second, maybe.
((I think it's that arcane connections don't reach across regio boundaries. If you're in a regio with Magic 5 (i.e. the regio side to the covenant) and try to use an Arcane Connection to Leap of the Homecoming to somewhere in Autun, it won't work. Or vice versa. I think.
((I noticed that this weekend...I suspect it's a function of the AutoComplete, because it did that to me when I was entering Learn Greek from the Teacher". I just fixed one of my colored backgrounds by clicking on the field I wanted cleared, click on "Format" at the top of the page, and then select "Clear formatting".))
Not in this saga. Some can Leap into the regio, if they have an AC. Pretty sure I've established this.