I believe, descended
Victor's workshop, he reported earlier (I:3:9), was a cell at the top of the house, separated in a complex way from the main part of the edifice. Presumably, the bedchamber to which he fled at the awakening of the Creature (I:4:3) was on a floor below. There the Creature wandered and awoke Victor who then in terror plunged outside. By some means unknown to Victor and unremembered by the Creature, the newly created being made his way from the house to the streets outside the courtyard, where Victor spent the night, and thence into the countryside surrounding Ingolstadt, where at last he fell asleep.