Beneath

Beneath my bright house
Beneath my red door
Beneath my white walls
There lies something more
A steep basement stair
That darkens each step
And there in the deep
My human heart's kept
An unspeakable thing
That's afraid of the light
An unthinkable thing
That makes noises at night
Few know it exists
And less dare to peek
All house guests beware
You'll find what you seek