I watch a classic film noir with some of my friends which has a scene where the hero draws a line on the pavements of a city - a continuous line that leads the other characters to various locations which helps to solve a crime or plays a role in attracting the femme fatal or something. My friend Ralph has the idea that we do out own version of this with black marker pens on the pavements of our home town. So we start drawing a long black line, taking an arbitrary route with a thick black marker. We get lost and head up dead ends or go full circle round the block, and end up having to cross lines or double-back. We are making a complete mess. We also have no mystery to solve - no femme fatal. There's no point to this - no narrative. Suddenly I feel terribly guilty about the mess we've made on the streets. "It will wash away in the rain" says Ralph. But I'm not so sure. "They are permanent markers!" I tell them. Ralph and Terry look sheepish now.