Cuckoo was coming. No one knew what it was; but everyone knew it was trouble. Designated Object Lambda when it first appeared on the fringes of the galaxy, 20,000 light-years away, it was traveling too fast, at one-sixth the speed of light. Astrophysicists said that it was vast, light-years across, improbably massless, and had the potential for utter destruction. So an existing space probe was reoriented to intercept it, and staffed with replicates, both humans and aliens. Then the space probe began to leak...