Every room keyed, every chest numbered: GM book pages 6 and 9.
Page 6. Scene 1, The Brass Kettle: Four stools at the bar. A key map of the inn with numbered spots: stairs up to the rooms, the kitchen, the trapdoor to the cellar and the front door. 1, The fireside. Where the heroes start, by Wenna's untouched tea. Nothing here bites. 2, The hearth. Warm stones. The coal scuttle at the end of them is a whelp, asleep in the heat. It fights with four or more players; with three it sleeps through. 3, The bar. Three painted stools and one plain one at the end. Nobody painted that one. 4, The tankard shelf. One tankard has a neat bite out of its rim, curved like the edge of a small lid. 5, The long table. Sawdust under the benches, and a trail of splinters to the kitchen. 6, The stairs. Up to the rooms. Tam's bed is unslept, his tin whistle on the pillow. 7, The kitchen. Oven, pantry, and the work table where the ham stood. The bread bin on it is a whelp; it fights only with five players. 8, The trapdoor. Nailed shut forty years ago by Wenna's grandfather. The nails are bent and standing proud, pushed up from below, and one board has sprung: there's a gap under it a flat hand wide. 9, The ale barrels. Teeth marks low on one barrel. Whatever tried it didn't like ale. 10, The front door. Over it, the iron hook where the brass kettle hung. Rain outside, and nowhere else open. Map key: a blue number is what's here; S the stool; C the scuttle, fights with 4+; B the bread bin, fights with 5. At 4th level count one more player (page 2). One square is 5 feet.
Spotting a whelp. A character who studies a piece of furniture can make a DC 15 Wisdom (Perception) check: on a success they see it breathing. Anyone who touches a whelp that fights at your table sticks to it (Grappled, escape DC 12) and is bitten at once: one Bite, before anyone rolls. Then lift its tent off, stand its teeth in the same square and roll initiative. Spotted before anyone touches it, it gets no free Bite.
Playing Wenna. Arms folded, pencil in her hair, voice flat as a tray. She never says she's worried; she polishes things. She counts everything: stools, spoons, heroes going down the cellar stair and coming back up. What they can keep. Nothing yet, and Wenna is counting. The bitten tankard is evidence; she'll let them take it. Tam's tin whistle goes back to Tam. What Wenna knows. Tam went to the kitchen about a noise just after closing. The kettle went Monday night: she heard it clang once. Her grandfather nailed the trapdoor and said what's down there is nobody's business. She's never heard of Ossery Vane, but she's seen a green cart with nice paint on the Fennick road after dark.
Page 9. Scene 2, The Cellar: Twelve chests. A key map of the cellar: stairs up to the Kettle, the vault, the wine bay, the back store and the door behind the rack, with the twelve chest spots, keyed as in the cellar key above. Map key: a blue number is a plain chest; a black number a whelp; a dashed black number a whelp only with more players (at 4th level count one more, page 2). One square is 5 feet.
Whelps. A character who studies a chest can make a DC 15 Wisdom (Perception) check: on a success they see it breathing. Anyone who touches a whelp sticks to it (Grappled, escape DC 12, Disadvantage on checks to escape). Lift its tent off, stand its teeth in the same square and roll initiative. The other whelps wake and hop in at 20 feet a turn. Vane's docket says live ones are chalk-marked underneath. True, but looking means tipping the chest over, and tipping a whelp means touching it.
Opening chests. None of them is locked. Opening one takes an action; when a player says which chest, find its number on this key before you answer. A plain chest just opens. Read out what's inside and let them take it. What they can keep. 120 sp and the hooded lantern (chest 10). The candlesticks and the good red are Wenna's, and she will notice. Tam's boot goes back to Tam.