The contents page of the magazine lists this feature as The Day. The title page of the comic lists it as The Day the City Crossed the Threshold. The threshold in question is a closet that the shop-owner has in the back of his shop that he tricks troublesome people into entering. Here we can see what terrors these victims have imagined for themselves in the closet.

Decent story and good art.

(Heavy Metal issue #14, May 1978 – Page 81 The Day (the City Crossed the Threshold) by Blanc and Dumont)