Continuity! Jack backstory! The little brother mentioned in "Kiss Kiss Bang Bang" by Captain John Hart makes an appearance as does the Boeshane Pennisula.
I absolutely loved that Jack was absolutely certain that Adam didn't belong because he didn't love him the way he did the rest of the team.
Martha Jones appears and the team seethes with curiosity. Loved the comments between Gwen and Martha that they must be the only two people on Earth Jack hasn't shagged and what were they doing wrong?
But the ending was a big shock. I'm on the edge of my seat waiting to find out what they do with that little development.