In these Oakland hills in northern California, the invader could have been a fox, a squirrel, or the usual raccoon or skunk. We have opossums, which do not move quickly no matter how alarmed. Some nights we hear a cougar scream in the woods, and one evening as Renato and I rounded the curve on our road, our headlights caught the green gleam of a cougar’s eyes. The distance between us was about 100 feet. Renato braked, and we sat still, staring. The lion was bigger than a German Shepherd, a tawny color, and its rounded shoulders as it sat were bigger than my own, or my husband’s for that matter. Its supple tail flew behind it as it ran off.