One late autumn night in 1227, Tranquillina and Gerulf are both in the Mons Electi library. Tranquillina has the cover open on one of the the giant tractatus written by Cannophori, its person-sized pages extremely unwieldy but containing many fine insights on the Art of Corpus. Gerulf is paying little attention to her when one of the covenfolk trots in to the library, respectfully waits for the maga's attention while breathing deeply, then says "The black rose is blooming, m'lady" in decent Latin. "That is good news, Mélanie," Tranquillina replies absently at first, "but why not tell the Aedilis? She will - ah, wait, Viscaria is no longer here, you should tell -" Without warning she stops speaking, looking thoughtfully over at the other magus in the room. Nodding to Mélanie, she walks politely over to Gerulf. "Sodalis ... has anybody taken you on a tour of the extended grounds of Mons Electi, and detailed the locations of its vis sources? - No? As I had feared ... I propose that you clear your schedule for tomorrow afternoon and evening. Come to my chambers after your midday meal."
The next day, Gerulf walks down a corridor of the mansion on the regio side*, one floor below ground level; the hallway has a single door in sight, which is currently open. Inside an opulently-furnished sitting room can be seen, with plush chairs and a lit fireplace. A young man is seated on one of the chairs, peering at a well-bound book with an illustration on each page. Tranquillina is nowhere to be seen, although the room has a door on the far side, marked with the sign of a maga's sanctum.
- ((Since you're somewhat new to Ars Magica, I'll err on the side of telling you too much rather than too little - apologies if I go over things you already know. A "regio" is a little pocket of supernatural reality, a little like an alternate dimension but usually quite limited in physical scope. Mons Electi has a huge mansion built in the mundane world, but at a spot where it's possible to enter quite a large Magic regio; there is an identically shaped mansion on the regio side, which is where most or all of the magi have their sancta and laboratories. See ArM5, page 189. A "sanctum" is the private domicile of a magus, typically containing sleeping quarters and a laboratory; by Hermetic law, anyone who steps foot into another magus's sanctum implicitly accepts any action the owner of the sanctum decides to take. See ArM5, pages 102 (top right corner) and 103 (top left corner).))
((PS: Do you have access to any of the ArM5 books besides the core rulebook? I don't want to refer you to something you wouldn't be able to read....))