What is the theme in The Beet Queen by Louise Erdrich?

Abandonment is a theme in the novel that begins, not with Mary and Karl, but with their mother, Adelaide. Adelaide is in love with a married man who pays for her home in exchange for being allowed to visit her as often as he can get away. When he dies, Adelaide finds herself homeless and penniless since her lover kept Adelaide's home in his name. Adelaide feels abandoned and desperate. Adelaide is also pregnant. Unable to fend for herself or her children, Adelaide abandons them just as her lover did her. Adelaide boards a plane for a ride and never returns.