a spider in its web

'There is a kind of net that is as old as Methuselah, as soft as a cobweb and as full of holes, yet it has retained its strength to this day. When a demon wearies of chasing after yesterdays or of going round in circles on a windmill, he can install himself inside a mirror. There he waits like a spider in its web, and the fly is certain to be caught.'

'Isaac Bashevis Singer, The Mirror from Gimpel the Fool and Other Stories, 1985.