I may have to come up with a quick 1-session story for a solo quaesitor. He's a mentem specialist with the gentle gift.
I'm thinking perhaps that a noble is rumored to have aquired a magic item, and the quaes is sent to find out if a mage is guilty of selling it to him. But not sure where to go from there.
Other suggestions welcome.
The problem with the idea as posted is that if the Quaesitor has something like Posing the Silent Question then the scenario could end pretty quickly, or alternatively have him chasing across the countryside on his own and therefore really quite vulnerable.
I've come across this problem before. Actually, it's probably quite common for troupes with Quaesitor characters.
My trick is to provide a mystery story. But one in which the killer/thief/antagonist is not necessarily there to be questioned. You need a balance. In your case you need some characters that are hiding something so that the Quaesitor can use his Mentem magic to find the truth. But those should be red-herrings. The main story should be something that can't simply be solved through a yes/no question.
If you have a subscription to Sub Rosa (and if not, why not?) then I'd recommend issue three. There's a story in there that might fit the bill...
Otherwise, although I can't send you any notes on the above story, if you pm me with your email address I can send some notes on another Quaesitor story I wrote (we have one in our troupe). It's a little specific to our saga but you should be able to see what I've done.
As another thought. Quaesitor adventures can be a little hard to involve the other characters in. But there are a couple of tricks that you can play.
Have the story set within the covenant. Make the other characters part of the investigation.
Have one or more of the other magi drafted in as specialists to help the Quaesitor, perhaps given temporary investigative powers.
Have the other troupe members play characters pertinent to the story. So, if the magus under investigation is being framed, he'll want to know by whom and for what reason. So give him to a player as a guest star.
If it's a major investigation, or a march or some such, then give the other players some hoplites or other Quaesitors to play.
It's useful to work out in advance how all the players will be involved as there's nothing worse than the Quaesitor player setting out without support because he can't justify involving his Tytalus covenant fellows in his investigation.
My suggestion is to have the Quaesitor track a potentially code-breaking mage. However, he's lead to an area with several magi, and the crime in question was committed by a mage who has the power, either through a breakthrough or from Faerie/Infernal sources, to prevent people from remembering any detail about him personally - his clothing, face, and voice are a complete blank.
So the Quaesitor cannot rely on simple mind-reading to solve the question.
I prefer Quaesitorial investigations that are more about moral dilemmas (strict interpretation of the Code vs. what "seems right"). Here's one I wrote for the troupe's Quaesitor a couple of years ago:
Maga K of Tytalus commissions Magus I of Verditius to craft an unusual dagger. The dagger is a gift for a local noble, who has agreed to sell a plot of land to her covenant. She stipulates very clearly that the dagger must be delivered by a certain time, as the noble is also considering a bid to a build a church on the land. Magus I agrees to the conditions, having plenty of time to fulfill the commission.
As part of service to the Tribunal, Magus I spends several seasons constructing items to defend against the Tribunal's enemies. This forces him to delay the construction of the dagger, though it is still completed with a few weeks to spare. One of his sodales, Magus C of Tremere, who happens to be travelling to Maga K's covenant on personal business, agrees to take her the dagger in return for a pawn of vis for his troubles.
On the way, Magus C camps for the night on the outskirts of a faerie wood. In the night, a band of faeries sneaks into the camp and steals the dagger, disappearing into the woods. Magus C attempts to retrieve the dagger, but he faeries prove impossible to track down. He returns to his covenant empty handed.
There is no time to craft a replacement item, and the noble, enraged at the failure of Maga K to fulfill her side of the deal, sells the land the church.
Maga K, who claims that Magus I has broken a bargain to which he freely agreed, declares that the vis site is failing, and demands Magus I pay the five pawns of vis per year that it used to generate.
Magus I is very concerned that, even if Maga K cannot enforce some penalty for the broken bargain, she will besmirch his reputation, of which he is very protective. He demands that Magus C, who failed to deliver the dagger, should recompense Maga K, or at the very least pay for the vis used to construct the dagger.
Magus C accepts that he failed to deliver the dagger, but offers to repay only the single pawn of vis he was paid, not the full price of the dagger nor the value of the lost vis site.
Magus I approaches the Quaesitor and asks him to investigate the circumstances of the loss. He agrees to abide by the Quaesitor's judgment, but lets it slip that if Maga K is dissatisfied by the ruling, he would agree to pay the five pawns per year rather than risk his reputation. Magus I is relatively young, and this arrangement would cause him severe hardship.
There is relatively little to "investigate" in this scenario; it is mainly designed to see what the Quaesitor regards as fair and whether that conflicts with Hermetic justice. One fact that may emerge is that Magus C and his grogs had been drinking heavily while they made camp and neglected to set a watch. Magus C won't admit this or allow his mind to be read, and he has told his grogs not to mention it if questioned. However, they are not particularly practiced at evasion and could be caught out by a skilled interrogator.
When we ran the scenario, it took a couple of hours in total. The PC Quaesitor, a former Traditionalist who had become much more pragmatic over the years, decided that the Magus I was responsible for crafting a replacement dagger for Maga K, though he was not responsible for compensating her for the loss of the vis site, as her further bargains were her own business. Magus I didn't like the judgment, but agreed to fully compensate Maga K rather than risk his reputation. Magus C repaid his single pawn of vis, and his (reckless?) drunkenness remained undiscovered.
Thanks everyone. Please keep 'em coming.
I'll be running a solo session for the guernicus. The other players can't make it, and the player is normally our Alpha Storyteller. He rarely uses a Beta, so I'll be stepping in only because the others can't make it.
Ruaridh, the above storyline is good, and I will mull it over. Thanks for writing it up. I'd love for a bit of "action" if possible. Not necessarily combat, but a sticky situation where magic is needed to extricate the mage.
The saga is set in Novgorod, and I was thinking of maybe borrowing something from the Rhine Tribunal book. Perhaps something to do with the Hanseatic league, Waddenzee, and/or Oculus Septionis. The russian redcap who lives at OS travels to Novgorod, and something happens on the way, which needs investigating. ahem... but what? I haven't gotten very far with that. Mainly, because the adventure needs to be self-contained. All of my ideas would stretch over many sessions.
I do have issue 3 of SubRosa, but haven't read it yet because I have been unable to get it open with my mac. I'll try to open it at work this week and see what's inside!
Thanks again, all,
eric
One of my current games (the face to face, not online one), my character is a mentem expert that has no hesitation to make people forget important pieces of information (loss of but a moment's memory). These can make trying to find the guilty party very hard. It requires research to get the image of the one that did the actual selling. You mihgt have to as questions for which way he traveleed to find buildings or peasants that actually saw the seller pass.
Come to think of it, a simple MuIm or MuCo can disguise the features to make identifying the seller hard too. The mentem can do a lot ot determine contacting method and other similiar things. Plus, whoever sold the permanent magic item needs tobe tracked down (or made it). If they are not of the order, perhaps they should be sworn ot the order.
There are several short adventures dealing with redcaps and code issues online. IIRC a pair of them (at least) are by Kevin hasall. Search for "online ars magica adventures" in google or yahoo and they should turn up. Nice to milk for ideas.
I LOVCE the adventure above, BTW. I think I might be stealing it straight away since we haven't had a hermetic low intensity adventure in a while. 
(we are currently on grand stuff dealing with davnalleus with our mages) . Thanks for sharing!
Cheers,
Xavi