"Flatline"

Jamie Mathieson's second story in as many weeks takes us to the land of trip-hop, where people are being turned into 2-D images. This, of course sounds very familiar. While it was not exactly bad, "Fear Her" was a very flawed story that rubbed a lot of fans the wrong way. To say that "Flatline" learns from the mistakes of its predecessor is something of an understatement...

The key reason for its success is that it is genuinely frightening. Unlike the Isolus, a fresh concept of an alien that was thoroughly explained and given a motivation for, the Boneless remain as inexplicable at the end as they were at the beginning. The Doctor muses as to whether their attacks are merely a means of communication by a race so fundamentally different from us (which recalls such illustrious precedents as Stanisław Lem's Fiasco) but, whether they want to conquer or communicate, they kill to do so and, in the end, they are monsters...and we know what happens to monsters. The way in which the plot unfolds is typical of so many 'using the enemy's power against them' stories – yet, when it is as well done as it is here, the results are joyous. The concepts are, on the surface, simple, yet they are irresistible – a miniature TARDIS with a full-sized Doctor carried in Clara's handbag is an idea for a series in its own right.

Douglas Mackinnon puts in another phenomenal turn in the director's chair with an embarrassment of memorably scary scenes – PC Forrest being flattened is brilliantly rendered. The 3-D realisation of the massive attack of the Boneless, starting with the shock of the giant hand snatching Al away, is awesome with their unsettlingly jerky motion of the shapes of the dead. However, Mackinnon also brings humour when needed, especially in the brilliant scene of the Doctor literally moving the TARDIS by hand, which manages to be both hilarious and exciting. Mackinnon and the production team also manage to convey the inimitable quality that Bristol possesses, a mixture of industrial grime and bucolic cosiness. The guest cast is hugely effective. Joivan Wade is great as tricky kid Rigsy and PC Forrest's awful fate is made all the more poignant with Jessica Hayles's plaintive screams. However, the best guest performance is that of character actor extraordinaire Christopher Fairbank, who makes the loathsome jobsworth Fenton into a truly memorable character.

As he appears throughout the story, it is easy to forget that this is a Doctor-lite story, but Peter Capaldi does not let his confinement to the TARDIS limit his performance – I particularly liked his happy dance when he (temporarily) saved the shrunken TARDIS. This leaves Clara basically playing the Doctor, something that Jenna Coleman does with relish.

"Flatline" is a fun, frightening and phenomenal tale that shows that Doctor Who can scare in a multitude of different ways, without becoming boring.

NEXT: "In the Forest of the Night"