By John Keegan and Paul PearsonThis is a tough one to assess. From the get-go, there's a sense of Big Things Happening in this episode and that's definitely borne out by the end, making "Barometz. Trick. Pressure." impossible to discount or ignore, yet the way it all comes together leaves a bad taste in the mouth. It's like the important exposition-packed chapter of a novel, but that doesn't necessarily translate to an episode of television, which still needs to be a self-contained story amidst the larger one, and it's on that front this instalment lets down the audience.