The cat eyes you for a few moments, and then speaks. "This is my master's hideaway-- I'm his familiar, G'arfeld. I can sense that you aren't lying about your cluelessness. How ever did you find this place?"
You recount your encounter with the strange clown, the cat nodding along- clearly intently listening, but lost in thought. "Another familiar perhaps? It doesn't seem like one of my master's creation, though. And you said he gave you a key, could you show me?"
You produce the key from your pocket and set it in front of the cat. He stands up, examines it, smells it, paws at it a bit, and then lays back down. "Curious, I've never seen any key resembling this one before." He pauses for a moment, and then continues, "it may be bad form for me as this place's sole protector, but please hold onto that key. Let me know if you find what it belongs to."