While environmental themes subtly weave through Sleator's previous works like The Night the Heads Came (1996, see separate entry, Vol 9), it is within The Beasties that these themes take center stage, driving the characters' actions and dilemmas. In this novel, a dedicated botanist whisks his family away to a sprawling house nestled deep within the heart of a vast forest for the summer, intent on delving into the world of fungi. Yet, the tranquility of nature is under threat as lumber companies relentlessly dismantle the forest, leaving behind barren slopes stripped of not just trees, but of life itself.

However, the forest refuses to surrender quietly. An unseen presence fights back against this deforestation, resulting in the sabotage of the lumber companies' machinery, and, gruesomely, individuals suffering unspeakable injuries—losing arms, legs, ears, noses—without a hint of disturbance until daylight. These chilling acts of resistance might be attributed to enigmatic entities, rumored to be the legendary "beasties," lurking in the folklore of those who dare to venture close.