If you weren't already on the edge of your seat for this fall's Doctor Who episodes, then this prequel to "Let's Kill Hitler" ought to do the trick.

This two-minute video reveals just what's really at stake for the Doctor and his companions as he rushes to fulfill the promise he made to Amy. It also gives us a terrible glimpse of a dark moment for the Doctor. And most of all, it does something that I've been missing from some of Steven Moffat's Who writing: It gives us a moment of genuine, honest emotion. God help us all if the Doctor can't keep his word.

Doctor Who comes back in just 12 days, on August 27.