The ruling on the ma'mum whose imam bowed before he finished al-Fatihah

If the ma'mum joins the prayer after the imam, and the imam bows before the ma'mum has finished al-Fatihah, should the ma'mum bow or finish reciting al-Fatihah?
If the ma'mum joins the prayer while the imam is about to bow, and the ma'mum is unable to recite al-Fatihah, then if only a verse or the like remains for him such that he can complete it and catch up with the imam in the bowing, that is good. Otherwise, he bows with the imam and he owes nothing.