At the end of the Doctor Who episode Blink, Sally Sparrow catches the Doctor and Martha running off towards an adventure. Are they running off to an adventure that occurs off screen or do we see this adventure in a later episode?
The adventure is off-screen, as we must assume that many are. Furthermore, and this is confirmed by the DVD commentary, the writers took the opportunity of making it sound like a peculiarly bizarre adventure, since they knew they weren't going to have to figure out how to show it to us.
SALLY: Doctor! Doctor! Doctor!
DOCTOR: Hello. Sorry, bit of a rush. There's a sort of thing happening. Fairly important we stop it.
SALLY: My God, it's you. It really is you. Oh, you don't remember me, do you?
(Martha is carrying a quiver of arrows, and the Doctor has a long bow.)
MARTHA: Doctor, we haven't got time for this. The migration's started.
DOCTOR: Look, sorry, I've got a bit of a complex life. Things don't always happen to me in quite the right order. Gets a bit confusing at times, especially at weddings. I'm rubbish at weddings, especially my own.
SALLY: Oh, my God, of course. You're a time traveller. It hasn't happened to you yet. None of it. It's still in your future.
DOCTOR: What hasn't happened?
MARTHA: Doctor, please. Twenty minutes to red hatching.
SALLY: It was me. Oh, for God's sake, it was me all along. You got it all from me.
DOCTOR: Got what?
SALLY: Okay, listen. One day you're going to get stuck in 1969. Make sure you've got this with you. You're going to need it.
(Sally hands her file of documents to the Doctor.)
DOCTOR: Yeah, listen, listen, got to dash. Things happening. Well, four things. Well, four things and a lizard.
SALLY: Okay. No worries. On you go. See you around some day.
DOCTOR: What was your name?
SALLY: Sally Sparrow.
DOCTOR: Good to meet you, Sally Sparrow.
Judging by the "lizard" part, I'm guessing there's a Silurian involved. We have no record of Martha ever meeting the Silurians, though. There are >>memes<< in the Internet linking it to "The Name of the Doctor" with Clara(1), River(2), Strax(3), Jenny(4), and Madame Vastra(lizard) => four things and a lizard. However, this...
1) doesn't account for the part of the red hatching
2) involves the 11th Doctor and
3) is long past the time of Martha's involvement with the Doctor.
We know this: There's likely five people involved besides the Doctor and Martha, one of which might be a Silurian. If "red hatching" is a code for something or at least not meant as an actual hatching of something red, it might be a sort of medieval festival, judging by the bow and arrows. One way or another, it's probably peaceful and doesn't involve danger the sort of which we frequently see the Doctor involved in.
But that's just my take on the whole idea.