So, the youth DnD group snuck into the house of Count Polyphemus Estudian to steal the book that he had written, which they were commissioned by the Library Lich to retrieve. The house is a largish manor sitting on a (possibly artificial) hilltop about a mile and a half outside of Daern something-or-other. (I don't remember. I made that one up on the fly; it's in my notes, but I'm not where I can look at those right now.)
After letting the Arcane Trickster scout the outside of the house with the help of his Cloak of the Bat, they decided on the simple and direct approach: they picked the locks on the front doors, and went in that way.
That let them into a two-story entry hall, with the sweeping staircases flanking an upstairs balcony; there were a pair of stuffed wolves on either side of the doors, and a pair of stuffed bears on either side of the far pair of doors (beneath the balcony). There were paintings along the walls, plenty of windows on the south wall, and it was generally all very dark and quiet. (Even with the windows, it's a bit hazy outside and it's only about 1/3 moon, so... not much in the way of natural light.)
The Arcane Trickster is a halfling, and he's using Goggles of Night Vision. The druid (also a halfling) converted herself to a spider and is riding around on his shoulder. The dragonborn sorcerer has taken advantage of his Ghost Cloak to become ethereal; he can see the group, but the only way they can talk to him is if the druid uses her Ghostwise Halfling telepathy and he happens to be standing in range. The swashbuckler/lore bard, like the arcane trickster, has been relying on her native skills for stealth.
So far, they have explored the ground-floor level of the entry hall -- where the swashbuckler's Rapier of Warning kept giving them oddly non-specific indications of danger -- and the dining hall, which was on the far side of the wall where the rapier indicated danger was nearby. The swashbuckler activated Detect Magic and looked over the entry hall but found no magic; she was pushing at the pictures to see if they were covering any empty spaces when her rapier twitched a warning at her. At that point they asked the sorcerer to go check our the room on the other side of that wall, which turned out to be the dining hall. (Of course, the rest of the group has no idea if he even heard them.) They discovered nothing threatening; in fact, so far everything was minimally secured and they saw no signs of life. (Admittedly, it's nearly midnight and anyone living here is likely to be asleep.)
While the sorcerer was checking out the dining room, the swashbuckler went to explore the connecting hallway on the first floor, behind the double doors at the back of the entry hall; she found several closed doors, and a narrower hallway leading towards the back of the house. The arcane trickster, meanwhile, started poking the pictures from a reasonably safe distance using Mage Hand.
When we ended the game, two major new developments had occurred:
-The swashbuckler's exploration of the narrower hallway had led her to a corridor somewhere near the back of the house, with doors on both sides. She could hear somebody snoring loudly behind one of the doors.
-The paintings in the entry hall were mostly landscapes, but the two northernmost were portraits, one of a man, one of a woman. When the arcane trickster poked the woman's portrait, the woman in the (apparently non-magical) picture turned and frowned at him.
Considerable discussion of the use and limitations of Detect Magic ensued, with a particular emphasis on how it related to shapechangers, spellcasters, illusions, and invisibility. I've promised to go do some checking up so I can give official in-game rulings on those things.