Beyond the Door
Dick, Philip K. "Beyond the Door." Fantastic Universe Jan. 1954. Coll. Collected Stories of Philip K. Dick (q.v. under Anthologies and Collections), vol. 2: Second Variety.
The cuckoo of a cuckoo clock dislikes a man who turns out, decorously, to be a cuckold. The man intends to destroy the cuckoo, "but it makes a pre-emptive strike" (M. J. Tolley 17, cited under Literary Criticism).