Jurgis and his family are just one of many in the vicious cycle of abuse which comprises life in Packingtown. Chapter 18 exists mostly to bridge one part of Jurgis' life to the next. Walking the wrong way after being released from prison illustrates the fact that Jurgis is directionless and clueless, yet still does not know to whom he should listen.
Arriving at his house, he finds that what he considered his own is, in reality, not his. Another family has been swindled, just as Jurgis had been. Both his house and his family are gone. Losing his house not only symbolizes the lost American dream, it foreshadows Jurgis' loss of Ona.
When he arrives to find Ona having an early and difficult delivery, readers know that this birth will not be a happy occasion and that Ona will probably die.
