A Beacon in the Dark

I was crouching behind the ceramic pot, clutching my folded grid paper... just staring at my three straight pebbles in the dim room light. Then, right beside my foot, I saw a tiny glass marble from a decorative dish, catching the streetlamp beam outside! It glowed like a tiny lantern! With both mittens shaking a bit, I nudged it between the first two pebbles. It clicked into place, throwing a neat little circle of pale light right across the painted sill. Now my outpost has its own boundary lamp... so I know exactly where the safe line ends before night takes over.