Maths and mystery add up to an unlikely but engrossing solution in Fermat’s Room, a Spanish locked-room teaser that handles its limited dramatic permutations with flair and skill. Four established mathematicians convene after receiving a mysterious invitation and then find themselves trapped inside a shrinking room. The only way to escape a grizzly death is to solve a bunch of maths riddles.

One of the invited is a 22-year-old maths phenomenon (Alejo Sauras) who’s the most likely to save his fellow ‘guests’ once the riddles start getting difficult. Also along for the numerical nightmare are an irritated inventor (Santi Millan), a pretty young genius (Elena Ballesteros), and a seasoned old maths wizard (Lluis Homar). Their host, of course, is called Fermat (veteran actor Federico Luppi). Facts begin to emerge about the protagonists’ past, the questions keep coming, and the walls keep closing in. Co-directors Luis Piedrahita and Rodrigo Sopeña exploit the limited dramatic space available to the maximum and the tension never slackens.