Drawn together by a mysterious host (Federico Luppi), four mathematicians wind up locked in a shrinking room and bombarded by a series of tricky riddles. To avoid horrific deaths, the frantic scholars must quickly figure out the link that unites them all. This engrossing Spanish thriller from filmmaking duo Luis Piedrahita and Rodrigo Sopeña stars Lluís Homar, Alejo Sauras, Elena Ballesteros and Santi Millán.