Complex sentence: Strangely, they haven't aged at all, and they have no clues about their missing time or their whereabouts during their missing years; however, they appear to be returning with compulsions to find certain objects and to continue their criminal habits.
Split into simpler sentences: Strangely, they haven't aged at all, and they have no clues about their missing time or their whereabouts during their missing years. The 63s appear to be returning without any memory of where they have been, but with compulsions to find certain objects and to continue their criminal habits.