内容简介：The Harn first came to the Warden's attention through its effect on the game population of an area in World 7 of the Warden's sector. A natural ecology was being maintained on World 7 as a control for experimental seedings of intelligent life-forms in other similar worlds. How the Harn got there, the Warden never knew. In its free-moving larval state, the Harn was a ticklike creature which might have sifted through a natural inter-dimensional rift; or it might have come through as a hitchhiker on some legitimate traveler, possibly even the Warden himself.