Tereza Nvotová's Nightsiren (Svetlonoc) was among the handful of titles that blew me away at this year's long-ago-feeling Boston Underground Film Festival. It's smart, beautiful, savage, and from a part of the world, Slovakia, with whose cinema I'm unfamiliar. (Ditto the filmmaking team of Nvotová and her co-writer, Barbora Namerova.) Part folk-horror and part female-empowerment/coming-of-age melodrama, Nightsiren demonstrates an ease with archetype and the courage to use funding provided by the Slovakian government to create a piece that questions the country's systems and traditions uncompromisingly. It's righteous.