Being left to her own devices while she waited for her nephew and neice-in-law to return, she amused herself by playing with the unusual toys Draco had.
Narcissa would be furious if she found his muggle section.
Something curious caught Bella's eye, and she approached the dim glow emanating from a peculiarly shaped object attached to the wall by a wire.
Close inspection did not reveal its purpose.
A Revelio didn't either.
Wand in hand and ready to react, she poked it.
Nothing.
Bella poked at it again.
It didn't look dangerous… and it didn't attack her when she poked it…
Becoming braver, the dark haired witch picked up Draco's glowing lava lamp.
She dropped it instinctively as the heat seared her hand. It hit the ground with a noticeable thud.
Damn. It must have some kind of heat-related protective spell on it.
The swirling bright blobs continued to float aimlessly inside the glass.
Bella didn't notice the crack that ran down the side, created by its impact on the hard wooden floorboards. Nor did she notice the heat engorge the crack as she silently waved her wand over her hand to heal it.
The sound of the front door slamming shut and faint voices in the foyer announcing Draco's arrival. About time too.
The first drop of luminescent liquid fell to the floor as Bella marched out of the room to greet the blonde young man.
Although the liquid alone would not have caused any harm beyond annoying Draco that his cool lamp was broken, the hairline fracture along the glass had grown to the very tip of the glass, to meet the crack in the plastic casing. The plastic casing which held the broken bulb and wires that powered the device. Wires still channelling an electric current without a purpose.
Fortunately, the electricity quickly found a purpose.
Uniting with the oily substance, still dripping and slowly encroaching across the wooden floor, with the speed and harmony of long lost lovers, a blinding spark ignited.
Within minutes the room was ablaze.