CLARIFICATION: The light was coming from the library and it is still on. An annoying flickering light that refuses to either go dark, short out, or turn fully on.
The camp fire is out and cool; the plentiful ash indicates that it has been in use recently. The sleeping bags are cool. Nothing appears to connect the mannikins. The barbie dolls are relatively new and have been cleaned, washed, dressed, and well looked after. The books are bent and yellowed: there are a mix of names of their inside covers - mostly from book banks and other places where such things are recycled.
Lina tries to find the source of the ozone stench, only to come to the conclusion it has permeated the air of the entire floor (maybe the full house). She cannot find a source, though she does find a room where the ceiling has been thoroughly smashed and electrical conduit hangs down like vines - still sparking. Yet the only "active" light is in the library.
The burning stain poses other problems. While the walls, ceiling, and floor are stained there are no immediate signs of fire damage.
While Lina examines the upper floor (finding no secret passages and figuring that either there is nothing to find or someone stripped anything of value - both mundane and possibly of Supernatural interest) Aaron tries to piece together the paucity of evidence.
There is something going on here. Floating through his mind are vague reports of similar finds: burn marks in wastelands far from human habitation just like what he finds in that room; a perfectly preserved room in a burned out shell with similar stains seared into it; rumours of a recording from an East European academy taken from a burning bush and then lost in a catastrophic fire...