creep across something
1. Lit. to move across something slowly and carefully; to sneak across something. The soldiers crept slowly across the rope bridge. The cat crept across the floor, stalking the mouse.
2. Fig. [for light, fog, etc.] to move slowly across a place or an area. A heavy fog crept across the coastal areas. The spotlight crept across the stage from one side to the other, as if looking for the performer.