Tha ain't supposed to go out when the skull moon is up. Tis dangerous and tha is likely to come a cropper.

At three in the morning on Tom Calver's thirty-fifth night in Hellsborough, his notebook had moved two inches and the chair had migrated six inches toward the counter where he stood every morning. The flat's system had been refining its model of him across thirty-five days — where he stood, not where he sat, since he had never sat in the chair. The handprint on the bedroom wall left by whoever had been in this flat before him was gone; in its place was his own, pressed from the inside during the hours the system assumed he wasn't watching.

yellow-wagtails wag their tails to draw prey close — the bioluminescent tip-pulse is barely perceptible in daylight, vivid in murk, and the creature positions itself at exactly the distance that reads as curious rather than alarming. Less noted: the wag frequency is a headcount. One pulse per two seconds means alone; faster means not. Twelve beats per minute, twelve wagtails nearby. Field note: the pulse is visible through closed eyelids. I discovered this by accident and have since declined further experiments.