The Tenant in the Vents

A lonely man, seeking a small break from his mundane life, decides to befriend a tiny spider on his windowsill. He feeds it, watching with a strange pride as it grows. But it doesn't stop growing. Now, a melon-sized horror stalks the air vents of his home, leaving gruesome gifts at his door. He created this monster, and now he's trapped with it. He hears it crawling, he feels it watching, and he knows its affection could be the death of him.