The Buzzing Wall Spring

I was prowling along the hallway baseboard when a shiny coiled spring stopped me in my tracks! It poked straight out of the wall, tipped with a little white rubber cap. Was it a hidden trap? I hesitated, held my breath, and leaned down to give the tip a sharp tap with my snout. BOING-G-G! The coil whipped into a frantic, shimmering blur! A loud hum rattled right through the hardwood, buzzing straight up into my foot claws! I scrambled back two paces and froze—did the wall just strike back?!