Another early Hammer flick from Terence Fisher, and it's far from his best, although not without elements of interest. Most of the time it adopts a stock approach, with stodgy plotting, a slow running time, and a lack of oomph that had me dozing off in the early scenes. The character work's okay but the plot's all over the place, feeling like an early sci fi flick at times but then becoming a mix of murder mystery and spy film. It's a shame it can never get going as there are some fun performances here, including from Eva Bartok and Alan Wheatley, and it does pick up towards the climax. Hammer wouldn't hit their sci-fi stride until they did THE QUATERMASS EXPERIMENT a couple of years later and never looked back.