This is part of a series of reviews of Doctor Who in chronological timeline order.

Previous Story: Towards Zero

Finally, the mystery is beginning to unravel. After being flung into so many random adventures with these characters, the Doctor has finally found one actually relevant to the characters themselves, who are capturing and researching their duplicates throughout time and space.

I expected more to be revealed here but by the end we don't learn much more than we already knew. It's just cool that the duplicates themselves were finally used as a plot device, rather than them just filling out the roles of other characters in these stories.

Next Story: Effect and Cause