Spoiler Level: Fairly High
Another Sarah Jane-lite episode, which always strikes me as odd since there are no Sarah Jane Adventures Christmas Specials.
Story wise, Sarah Jane being missing works fine; Rani and Clyde wake up and discover they are the last two people on Earth. Their search for anyone else leads them to a young boy named Gavin, the only other person on Earth who hasn't vanished. Rani & Clyde then try to figure out what pattern there could possibly be between the three of them, since both Rani & Clyde have had all kinds of amazing things happen to them but Gavin has led a normal life. Then a couple of robots show up and start chasing them around a lot.
The story itself is pretty good, although everyone spends way too much time wandering around yelling "What's going on?!?" in the first episode. They do eventually start hunkering down and putting their minds to the problem to try and figure it out, which gets the plot moving, but with only three characters (and two robots) for the entire cast it takes a while. On the plus side, it's also an opportunity to have Clyde and Rani spend a lot of time alone together and gives their blossoming romance a chance to unfold a little further. The fact that they may be the new Adam & Eve is brought up more than once.
The resolution was completely different than what I had theorized it would be, which I was quite pleased about. It tied the whole story together quite well and provided some very interesting answers to all the questions that were raised. Another very good story, even if Sarah Jane herself was barely in it!