Well... Nope, it's not an illusion, or a bit of paper on the blade. It's actually a chip in the edge.
The exciting story:
One afternoon, not long ago, I was exploring an abandoned factory building here in Philadelphia. The old monster has been disused for several decades now, slowly sliding back into the landscape, becoming more like a pile of rubble each day. Most of the old glass is missing from the window panes now, and the sunlight streams in at crazy angles, illuminating the interior in a mottled fashion, with a sort of insane, fun-house effect. As I worked my way through the corridors and onto the main factory floor, stepping over piles of rubbish and dead rodents, I noticed a staircase tilting wildly up to a catwalk that ran along the walls, at about second story height. As I ventured toward the staircase, to snap a photo of the twisted metal that rose into the darkness, a sudden CLANGGGG issued from the shadows. With a violent heave and an ear-splitting screech, the rusty steel stairs broke free from the wall, and began to lean toward me. As I scrambled for my footing amidst the crud that littered the floor, I knew I was not going to escape unscathed. As if in slow motion, the contraption came down upon me, knocking me down and pinning my left leg against the crumbling concrete. Slowly, the dust settled as I regained my composure and bearings. Trapped! Alone! The feral kitties began circling, eager to feast upon my disabled carcass. I knew I had to act, and fast. From my restricted position, it was difficult for me to see an easy way out. But wait! Here, in one spot, some water dripping from the leaky roof had caused the steel beam to rust nearly all the way through! Oh, sweet providence! So, from my jeans pocket, I drew my trusty Charlow. Gritting my teeth against the grinding of steel on ferrous oxide, I slowly chipped away at the rust. Bit by bit, I worked at it, pausing only to flail my arms about, waving my blade at the advancing kittens. Back! Back, I say! An eternity passed, and finally, *TINGGG* my blade passed through a gap in the metal. I mustered all of my dwindling energy to heave the broken beam off of my mangled leg, and dragged myself to the doorway. Using the walls for support, I hobbled back down the corridor, and back out into the twilight of the evening. Free! Alive! Safe (mostly)! I pulled my Charlow once again from my pocket, held it up at eye level, and gave it a kiss of gratitude. I opened the blade, to examine the edge, and much to my dismay, saw that it had sustained a chip from hacking through the rusty metal. Oh, cruel fate! Ah, but a small price to pay, for another day above ground!
The less exciting story:
In the kitchen, I was standing at the counter, touching up the edge of my Charlow on a pocket stone. My wife was putting away a serving bowl on the shelf above me. "Would you like me to do that for you?" I queried. "No thanks, I've got it," was her reply. WHANGG! CRASH! The bowl slipped from her grasp, being still damp from washing. It tumbled toward my 'work space' and I reached out to grab it.... at the same time letting go of the other things in my hands. Those things happened to be... My pocket stone, and my Charlow. They tumbled to the hard tile floor, and landed among one another in a jumble. Upon retrieving my beloved barlow from the baseboard, I was bummed to behold a broken blade. Bah!
So... pick a story, if you like, whichever makes you feel better.

I like the first one, personally.