A solid if unremarkable Eighth Doctor story. It concerns the Eighth Doctor and his companion Charley Pollard receiving a cryptic message from the Eleventh Doctor: the Doctor's future incarnation is in a pickle, and William Tell is the key to solving his predicament, but they must watch out for the 'enemy aliens'...

The Eleventh Doctor gets a little more to do in this beyond each Doctor simply finding recorded messages, which is nice; it's great to see him be a part of the resolution.

It's a bit of a slow story though, with most of the narrative occurring in the last fifteen mins; I like the ambiguity of the ending (which reminded me of the later TV ep Deep Breath), and the narration by India Fisher is brilliant, but I feel like the story could have kicked into gear sooner. It takes a very long time for the aliens to actually show up, and the whole plot with the Doctor and Charley being framed for murder doesn't really go anywhere.