At first blush, the 1900s’ Return of the Century sounds like a neo-folk-rock classic, adorned with winsome vocal harmonies, chiming guitars and bittersweet melodies. But there are darker, more mysterious aspects to this Chicago indie-combo’s sophomore album that sink in after the surface sweetness wins the listener over. The band — now slimmed down to a sextet — weaves vignettes of romantic dysfunction and spiritual domination into its elegantly nuanced tunes. Singers Edward Anderson, Caroline Donovan and Jeanine O’Toole offer these songs with an earnest yet melancholy air, accented by Andra Kulans’ violin flourishes. “Amulet,” “Lay a Ghost” and “Zerkalo” wrap elliptical lyrics around honeyed hooks, creating a pleasantly unsettling atmosphere. “Lions Fur” is a particularly good example of what the 1900s do best — vaguely tropical in sound, it combines a cascading tune with nervous observations about life’s boundaries. “Overreactin’” drapes rippling strings over a silken groove, while “Jean Demon” basks in ethereal orchestration.