Framed: Mystery/Spec-fic

I was returning from my alibi, feeling rather smug and a bit nervous at the same time, when some kid darted up from behind me, bumped into my hip, and bolted off down the alley in front of me. My hand went reflexively to my pocket. I felt the familiar bump of my wallet--but there was something else there, too. Something long and heavy that didn't really fit in my coat. It was an oddly familiar feeling. I pulled out the foreign item and gaped at it. It was my knife, my bloodstained knife. Except it wasn't my knife. My knife (now safely sunk to the bottom of the river) had a little notch high up on the handle, where my uncle had tossed it too hard against the tools in his workroom. This one didn't. But the handle type, the blade, everything was the same. And it was covered in blood, and now, so were my hands. And my coat. I'd be conspicuous without a coat in the cool November air, but better that than a coat covered in who-knows-whose blood (although I began to have a suspicion). I shoved the knife back in my pocket and put my hand over it to hold it there as best I could, and I ran after the kid. It had taken me too long. By the time I entered the alleyway, he was long gone, leaving no sign as to which way he'd gone. Probably for the best. I'm pretty sure I wouldn't have hurt a kid, even one trying to set me up, but I had a knife in my pocket and anger was heating up the back of my neck and blurring my vision. I'd had a good plan, damn it. I'd been in the clear. Now I most definitely wasn't, and there was probably more that I didn't even anticipate. Then I saw the folded note laying in the center of the alley.


Inspiration: Evan's post: "Please never use 'framed for a crime (pronoun) didn't commit.' That's what being framed is. 'Framed for a murder...' works; it adds information." Plus a Writer's Digest prompt about a kid disappearing in an alley and leaving a note behind.
Story potential: High.
Notes: Could be fun. Could also play it as straight mystery or toss in some spec-fic elements.